(Crossposted from FurAffinity and my nsfw tumblr)

Disclaimer

I'm no authority and these aren't rules, they don't apply to all situations. Etiquette is a common code of polite behaviour designed to avoid unnecessary conflict, but it doesn't always go far enough and it often goes too far. I think the best case is that this guide informs your better judgement.

Preparation

• Some artists use Trello to organise their work. It's actually great for commissioners too! Here’s one of many ways you can keep a commissioner’s board: https://trello.com/b/TAYg0ZBq/commissions
• Keep a list of commission ideas. It can be really helpful for diving into quick sales, but thinking ahead also lets you develop an idea and gather useful references.
• Always read the artist's terms of service to know what you're getting. If you're commissioning a private and tender moment between you and a loved one, you might not want to see prints of it being sold at conventions. You might also be expecting a high-res version for personal use. Never assume. An artist's terms are there to protect them and you.
• Know what you're getting into. Don't assume that you'll get your art within a couple of weeks of paying; read the artist's journals to get a feel for how they work and what situation they're in. Some artists take months to turn a commission around, some of them are working through personal issues. Life happens, and people in a bad situation don't get many opportunities for good luck to happen. That doesn't mean you shouldn't commission them, it means you shouldn't add to their problems by getting upset when they fail to meet your unrealistic expectations.

Commissioning

• If you have a very particular composition in mind, ask for (or provide!) a "stick-figure", "outline" or "thumbnail" WIP. Unsurprisingly most artists are imaginative and visual thinkers, so text descriptions rarely get interpreted the way you might think. Send references if you can; Google image search is an obvious choice, but there's also a huge treasure-trove of anatomical, pose and character references at http://pinterest.com/characterdesigh/ if you're stuck for ideas.
• If you expect a certain turnaround, make sure the artist agrees with it. Some artists actually prefer being given deadlines, but most don't.
• Don't pester even if you're in the right. If you've not had any word from an artist for a while, it's reasonable to nudge once or twice, but "a while" means something different for each artist. If you do nudge, be polite and understanding. Communication between an artist and commissioner is often welcomed by artists, but never presume a commission relationship is equal to an offer of friendship with all the demands on their time which that would confer. Keep contact light, friendly and constructive, and if you end up making friends over it then that's great for both of you.
• Text descriptions are are a lot more ambiguous than you probably realise, so get a ref-sheet, especially if your character has specific details that are meaningful to you. Make sure you're explicit about small details that matter to you, e.g. piercings, shaped markings, etc.
• If you have complex markings, wings, tentacles, or specific details, then expect to pay sparkletax. It might not seem fair to you, but they're usually a lot of extra work. And on the other hand, if you're happy for an artist to experiment with your character's design or clothing, say so!
• It’s great to provide references for poses or backgrounds and even colours or moods, but don’t ask artists to make something exactly the same as the images you provide - photographic or artwork. Aside from the obvious storm of drama and accusations of tracing that this invites, it also denies artists the chance to be creative and devalues their skills. It’s also kind of weird and rude to ask a furry artist to draw in another furry artist’s style.

Reviewing

• Ask for changes before inking and colouring, don't expect changes afterwards. Send all your changes in one batch. And wait at least half an hour before hitting the send button. I've lost count of the number of times I've either spotted something else, or discovered that a change I wanted didn't need changing at all.
• When an artist sends you a WIP, give yourself enough time to spot changes. If you're experienced and have a good eye for anatomy, that could be as little as a few minutes, but more likely you should look at it critically, then come back to it a few hours later. Flipping the image horizontally is a simple way to give yourself a fresh look at an image without having to wait too long. And remember, if an artist can keep working on other slots while you're reviewing, you're also giving them time to look at your work with fresh eyes when they come back to it. Time is a precious resource for artists; give them enough to stretch themselves.
• Keep changes to a minimum. Proposing a small anatomical fix or pointing out missing piercings is one thing; asking for a different angle or pose is another thing entirely. This is why references and thumbnail sketches are so important if you have a specific image in mind.
• Show what you mean when you want a change. Artists are usually visual thinkers, so highlight areas you're not sure about and send a dropbox link or put it on imgur or something. And be helpful but not demanding - offering a redlined fix is great if you've got the eye for it. Trust their judgement if they disagree, and accept that some changes are too big to do anything about this time around.
• Furry art is not an industrial process. No one churns out consistently good art (despite what you might see in a gallery), so don't expect perfection. Accept that some jobs are more challenging than others and sometimes the planets just aren't aligned right for your particular piece. There's always the next time.
• Artists are their own worst critics; I'm not saying they're precious snowflakes whose feelings need preserving at a cost of your own happiness (that usually ends up with both of you being unhappy), but don't compete with their inner demons. Always be constructive with your criticism, and put at least as much effort into telling them what you're happy with as what you have concerns about - if you say nothing, then many artists assume the worst. Being gracious, patient and generous pays back in this commission and every one that follows.

Money

• We’ve all been there; that artist who’s never open for commissions suddenly has slots available, but you aren’t paid until next week. Or it’s like $30 more than you have right now. Stop. There’ll always be other slots opening and other awesome artists to commission. Put money aside for commissions and don't spend more than you can spare. Remember that it’s a lot easier to put a few dollars aside on payday than at the end of the month.
• It's rude to complain about an artist's prices in public (especially on their gallery or journals). If you can’t afford it, that sucks, but that doesn’t mean it’s overpriced. It’s common for furry art to cost between $30-50 and take 3-5 hours to complete; could you live on $10/hour? Can you get health insurance and feed yourself on that?
• Some artists get in trouble and offer "doodles for donations". Be generous, but remember these are not commissions; if you expect anything more than gratitude in return, chances are you'll be disappointed.
• You might think you’re being helpful by sending a payment as friend/family instead of as "goods/services", but Paypal can be total dicks about accounts which have dozens of friend/family payments coming in from various places (freezing or closing accounts, etc), and you lose any kind of payment protection if things go wrong. If you really want to be nice, throw a couple of dollars on top of the asking price to cover fees instead, but don't say in the payment notes that you've done this because it's against Paypal's terms for artists to charge more to cover fees. Mentioning Furaffinity in the payment notes can also cause problems, so don't do that.
• Tipping’s part of the culture in the US, so it’s surprising it’s not more widespread in the furry art world. If you can afford to, tip, especially if you got more than you expected, if the work was done really quick, or the artist was super nice.
• If the price was low, tip high. The market on FA is pretty tough for beginner artists to get into; when artists are starting out they're competing at the bottom end of the price range with people who can kick out 2-3 times more work than them in the same time. If you end up paying $15 for a commission you love (and you can afford to), tip another $15. You’ll make the artist’s day and you’re still getting a bargain.