Just because you're a beginning artist doesn't mean you don't deserve compensation for your time. There's a lot of companies or independent projects out there who want to lure beginners into doing tons of free art for the "exposure" and a lot of it is because they know that kind of shit won't fly with a seasoned artist. They know how ridiculous it is to even ask so they don't bother asking someone who'd know what they're up to. And a lot of times there are really really talented folks, people who blow me out of the water with their works who undersell themselves or practically give their art away because they haven't gotten "out there" yet and don't realize their talent is worth anything. It's a cryin' shame.
You can get plenty of exposure by doing paid works, even if its very little pay, but at least cover your materials. Why settle for something that will probably go nowhere (and a lot of these types of independent projects do, sad to say). There's nothing wrong with doing pro bono work if its not expected by the company and you think it /would/ be a good idea to just get your foot in the door provided you think that there will be paid work in the future or good contacts (or if you really don't mind working like a dog for free on a regular basis), or if that's your thing, but this is not what this rant is about, its about the people who know they should be charging but don't anyways because they're being lied to by cheapasses who intentionally want to take advantage of them.
If you sincerely don't mind giving away your art, or youre doing it as a favor to a friend, charity (which is just out of the goodness of your heart anyways) then go ahead, but don't for one minute think that you don't deserve some form of compensation on a serious project, even if its being taken out to lunch, because you're not experienced enough.
Red flags go up when the project is presented in a professional manner but when asked what it pays the answer is something along the lines of "Looking for desperate/beginner/students to get their foot in the door" or "It's more a labor of love and is on a limited budget" (I've gotten that one before, if they didn't plan artistry into their budget they shouldn't even ask) "The reward is that you'll get your name on the website/project/newspaper/credits" etc etc the whole song and dance. Another one is that they'll skirt the issue altogether until asked several times.
Your time is worth something. Bottom line if you plan to sell your art, you should be paid /something/. Makes sense, no? You wouldn't ask a mechanic to work for free, or to "tighten a few lugnuts and if you like what you see you'll pay him on a future overhaul if you should ever need one". They know that overhaul probably won't ever come.
And to those who have ever said those magical words "Well I was hoping to get this for free" or any of the aforementioned excuses for non-payment ...shaaaaaaame on you. Shaaaaaame. *wags finger* I sincerely hope no one ever takes advantage of you when you're learning a new skill. That's like teaching someone how to play chess and totally beating them their first game and pointing and laughing in their face that they're so bad. Just because they're new to the professionalism of art doesn't mean they eat less and have no rent to pay, nor does it mean that they're "easy pickin's" to sneak in under the watchful eyes of the rest of the professional world who wouldn't give you the time of day for your ludicrous request. We look out for our own, you know, and people talk. You know what you're doing by asking that, we're not stupid.
Note: It is perfectly legitimate to look to a beginner or student for /cheaper/ art, especially since oftentimes they don't want to have a huge monetary liability when they're still "feeling their way around the business", but to ask that they slave away for free right off the bat and balk that they charge /anything/ is really shitty.