Although this may seem pretty obvious, joining the guild can often be a rather painful process, given where the guild is located. Your best bet is to use the in game DIR system in order to find it, since it's on the outside of town, past the Middens. Simply do a DIR MOON and you'll get to the front door. Now, in order to actually become a guilded moon mage, you must find the guildleader Kssarh, who is actually on the third level of the Moon Mage Guild. Since it's considered an in game secret, I won't give it entirely away, but you will need to use some stairs and there will be a pedestal which will help get you in to see Kssarh. Once you're all joined up, follow the reverse path and you ought to be fine in getting out.

Moon mages are a magic primary with survival and lore secondary guild, meaning that a good deal of your time will be spent practicing the various magics, particularly power perception, primary magic and harness, with lesser emphasis on magical devices and targeted magic. There is a pretty hard survival requirement, though it's not particularly daunting in comparison to some other guilds, as you do have control over which of the survival skills you want to train and the requirements are more plentiful than particularly challenging. The lore requirements are mostly stuck on teaching, scholarship and the Moon Mage only skill, astrology, with an optional lore skill of your choice. It's usually a good idea to choose a relatively easy and useful skill as your option, such as appraisal or mechanical lore, but using an instrument should also be acceptable.
Perhaps a boon to being a moon mage is that there is no hunting requirement, which means that you needn't train weapons or armor if you do not want to. This doesn't mean that you can't be an extremely successful hunter, it just means that you aren't required to hunt if you don't want to and that you're given more flexibility for circling. Given that moon mages do have a number of very potent offensive spells and that they are able to learn evasion at least fairly well, hunting can be fun, but be forewarned that armor and parry and weapon skills will move very slowly after a while.

Moon mages, being armor tertiary, do not have a lot of flexibility with respect to working down hindrance in armors. While many moon mages may decide to work their strength up considerably, a majority of them will keep fairly low strength, meaning that choosing a lighter, less encumbering armor is the best choice. Also, being survival secondary, evasion tends to be the primary defense and having an armor which has low hindrance is a substantial benefit.

Heavy or Light Plate would be best avoided, as they do provide good protection, but at substantial hindrance and weight costs.

Heavy or Light Chain seems to be the best bet. Light Chain will tend to have slightly less hindrance and so is a better choice than Heavy Chain, but both are suitable for moon mages, due to their relatively low weights, high protection values and low hindrance.

Leather is another good choice for moonies, due to its fairly low weights and very low hindrances. If you're not going to hunt most of your time and just want something to protect you while sit back at missile rang slinging spells, this may indeed be the best choice.

Weapons are an optional thing for moon mages and, as always, a very personal choice on what's best for you.

Edges probably provide the best all around value as a weapon. Light edge is probably the least favorite, since its damage is usually quite low and it's possible to get low RT on bigger, more damaging weapons, in a short amount of time. Medium edge is arguably the best choice for a moon mage, as the Moonblade spell creates a magical medium edged type weapon which can be useful for several things. Also, medium edged comes in both jabbing and a slicing models. Heavy and two-handed edged also make good choices. If you're looking for more damage at the cost of RT, then these might be the best for you.

Ranged weapons are a little redundant for a moon mage, since spells often take care of needing to damage from afar, but there is always room for doing damage from long range when your mana runs out. Currently, longbow offers the best of all worlds when it comes to ranged weapons; manageable RT, cheap and plentiful ammunition, lots of damage. This may change in the future, however, so the longbow may not always remain the end-all be-all of ranged weaponry. Heavy or Light Crossbow can be a nice choice in an emergency, since you're able to get off a quick shot while your mana replenishes, hopefully long enough to stall your enemy.

Multiple opponent and parry are useful skill for all guilds, but will be difficult for moon mages to learn. A moon mage's best defense is a good offense, so while learning parry will naturally come from hunting, it's doubtful that you'll need to pay special attention to training these.

Six to eight survival skills are required to advance as a moon mage and so should be chosen wisely while young.

Evasion is a very useful survival skill to train and crucial if you intend to hunt. Should your choice as a moon mage be to hunt often, you can't go wrong choosing this as one of your survival skills.

Climbing is an easy to learn skill as well as a useful utility while moving about the realms. Given its ease of learning and that it doesn't require you to enter combat, one should train this skill, even if it's not one of the primaries.

Perception would probably be considered by most moon mages to be their most important survival skill, since it can help a great deal in observations. It's highly recommended that you train perception as one of your circling requirements. JUGGLE is a good way to learn this, as is foraging and disarming.

Hiding and stalking ostensibly seem like skills which don't require hunting, but after a short while, methods of learning these skills out of combat will diminish. If you intend to learn one of these, you may as well learn both, and if you intend to hunt a fair amount, you may as well choose both of these. Learning hiding by hiding from critters at missile range, pole range or even at melee if they're otherwise engaged is a splendid way of learning the hiding skill. Stalking is learning by the approach from missile to melee while being hiding and by using the stalk verb while in hiding.

Disarm and lockpicking again require that you spend a fair amount of your time hunting and often require that you move around between provinces a lot in order to find critters which are dropping boxes that are in your skill range. These are fairly finicky skills and will require a fair amount of patience and tolerance on your part to try and learn.

First Aid is a very helpful skill and it would be a mistake to completely ignore it, even if it isn't one of your top skills. The best way to learn is to tend someone else's bleeder, or to keep one yourself, with the latter method being risky due to disease. Blood worms will also teach a fair amount of first aid, but you should have at least 100 ranks before you deal with those.

Foraging was, for a long time, one of the worst skills in game due to its completely painful learning process. Thankfully this has changed and it has become a very learnable and useful skill, as it allows one to find healing herbs as well as items for learning other skills. Many would argue that this is not a good choice for moon mages to learn, but given how simple it is to lock and that it doesn't require combat, it should be given consideration. Moon mages, being survival secondary, are given access to FORAGE CAREFUL, opening up learning and potency of herb potential that not many others have.

Skinning requires you to hunt. A lot. If you intend to be a hunter, chose this and skin everything you hunt that's skinnable, then take their hides or skins or pelts back and scrape them for both skinning and mech lore experience.

Swimming is a skill somewhat similar to foraging, in that it was once a fairly difficult skill to learn, but is now quite the opposite. It doesn't require one to hunt, doesn't require any special gear or time, but may require the moon mage to move in order to find better swimming spots.

With a hard astrology, teaching and scholarship requirement, a good deal of a moon mage's time will be spent in scholarly pursuits.

Teaching is accomplished through the one tried and true method; teaching. Basically, you're stuck listening to classes or teaching others in order to learn this skill. It's time consuming, but it's pretty easy.

Scholarship is primarily learned through listening to classes on any subject, including scholarship itself. In addition to just listening to classes in order to learn it, one can STUDY embroidery patterns or spellbooks. Origami is also a good, though not outstanding, method of learning.

Astrology is the moon mage's unique skill and is integral to circling and using most moon mage abilities. While young, learning astrology is most easily accomplished by using OBSERVE on all of the constellations in the sky, which is determined by using OBSERVE SKY and using the PREDICT WEATHER ability. It's a little slow going, but it gets there.

Mechanical Lore should be trained if you intend to do enchanting later on, like making gweths or celestial jewelry. Easy ways of learning this are to CARVE branches and to BRAID grass or vines. Those methods will teach you to at least 100 ranks of mech, at which point you can start to worry about whether or not you should be using origami.

Appraisal can be learned by appraising just about everything. Appraising armor and weapons tends to work a bit better than fluff and appraising gem pouches, tilting toward full, teaches even better. Appraising creatures in combat, once you have enough skill, is also an excellent way of learning. Appraisal is a nice all around skill to have and it's best to train this in addition to mechanical lore.

Instruments don't have much use and if you want to train them, be prepared to spend a lot of time, money and effort in keeping your skill going.

Well, here it is, the moon mage's ultimate skill set. You must train magic in general as well as power perception in specific. Early on, you're best of learning most of your general magic through primary magic and harnessing and supplementing it more and more with targeted and devices.

Primary Magic is easy to learn at almost any level and just requires time be spent in casting spells over and over. Some spells teach better than others, but when you're young, picking shadows and clear vision is a good idea, since they're pretty easy to cast and teach reasonably at low levels.

Harness Ability is learned along with primary magic simply by casting spells. You can also get harness going by using cambrinth while trying to learn magical devices. Basically this skill is learned in conjunction with learning those two other skills and you shouldn't worry too much about trying to raise this skill specifically.

Power Perception is supposedly the moon mage's hallmark magic skill, but is indeed mostly just a pain and not useful for moonies yet. Even at high ranks, power perception is less useful for a moon mage than for any other guild, but it is required and it does help a little, so check out the moon mage power perception page for more detail.

Magical Devices can be a frustrating to learn until you get 20 or so ranks under your belt. Using FOCUS on runestones and CHARGE and FOCUS on cambrinth are really the only ways to go about it. Using runestones is concentration dependent and so it may require that you have a decent disciple stat and a couple of circles under your belt in order to work how you'd like. Another good way of learning it is if you choose the moonblade spell, you can FOCUS MY MOONBLADE repeatedly and lock magical devices in pretty short order.

Targeted Magic is used in combat and so will probably only be of use to you if you're going to be a combat moonie. If this is your intention, the telekinetic throw (tkt) spell is recommended, as it's easy to cast and teaches some targeting.