Here are some handy guidelines for how to write good art requests.  These aren't hard and fast rules, but if you're looking to get responses, it helps to follow them.

The basics:

• Tell us what your game is about.  This might seem obvious, but some people don't do it. :)
• Tell us what style of art you're looking for.
• We don't have any issue with art requests for non open source games here, but whether or not your game is open source does factor in to some of our users' decisions as to whether to work on your request.  If you don't specify, people are going to ask or assume that you're not, so it's nicer just to let us know up front. :)
• Note that we can't entertain requests for help with IP (intellectual property) that you don't have a license to use.  That is, if you're looking for help making a fan game, we probably can't help you, unless a) you need help completely replacing ripped art and IP with original work, or b) you're making a fan game of some content that explicitly allows fan games to be made (such as open source games, or certain not-strictly-speaking open IP where the owner has specifically allowed the creation of fan content).  This applies to both commercial and non-commercial games as well.  (While it's true that making money from a fan game will probably get you sued faster, it's still against copyright law to redistribute someone else's IP, even noncommercially, without permission.)

Also, I'll be honest here.  If you and your friend are just starting a big MMO project and maybe you've got a terrain engine written, that doesn't mean you're ready for art.  There are a lot of really ambitious projects that never go anywhere, and artists who have been around for a while are used to hearing requests like this.  Everyone thinks their big project is different from all the other ones.  You need to be able to prove it in some way.  If you have an ambitious project and you want people to help you out, I recommend the following:

• Have several hours of real gameplay.  This isn't just wandering around randomly generated terrain.  Real quests, real NPCs, real levels, boss fights, whatever.  The art can look horrible, but if you're asking people to work on your project out of the blue and you're not already established, you need to be prepared to show people that their art will be put to good use.  "Several hours" is of course a rough statement based on the game being large and ambitious.  Obviously if it's a puzzle game or a fighter or a simple shooter that is never intended to have several hours of gameplay, then you just want to provide a good amount of gameplay to prove that you're dedicated and able to finish your project.
• Yes, free art internships are a real thing, and some artists do them.  But if you have to post on OGA looking for art interns, then your company isn't big enough to matter on anyone's art resume.  "It will look good on your resume" really only counts if the people reading the resume have heard of the company in question.
• Of course, it also looks good on an artist's resume to have art in a finished game, but this goes back to the bit about having actual gameplay.  Most game projects fail, and as an artist, doing pro bono work for a project that doesn't have any gameplay is a huge risk.
• If you're asking people to do work for free, meeting them part way isn't good enough.  Don't make artists do extra work just to figure out what it is they need to do for your project.  Be prepared to ask for specifics.
• Offer money (this will work even if you don't have real gameplay).  And I mean real money, not just "hey, I'll give you fifty bucks to do all the art for my huge game."  If you want to pay artists to do your work, you need to consider something along the lines of $12/hour minimum even for a student artist.  Bear in mind that a typical pixel sprite sheet or tile map is $100 on the low end (for something low spec done cheaply) and a typical 3d character is probably going to be upwards of $1000.
• If you don't have gameplay yet, you can probably get a decent stack of concept sketches for $100-$200.   Concept sketches provide a good starting point and help you determine an artistic direction early on with minimal investment before you get deep into coding.
• If you can't pay and you want people to work on your project for free and you don't have any appreciable gameplay, sometimes artists can be convinced to help if you ask for openly-licensed art assets that will be useful for other projects in addition to yours.

And just a final note: If you're asking for more than a tiny bit of art, these guidelines go for everyone.  Every team believes that their project is different, or they wouldn't be working on that project.  And I'm not saying that your project isn't different, just that since pretty much everyone is claiming to be different you need to be prepared to prove it with more than just talk.