The way I price mine is: how long do they take me to do X what I want to make per hour. When I was just starting out I paid myself $10/hr. I promoted commissions that on average took me about 3 hours, so I charged around $30.
I found that as I got better I got faster, meaning my rate of pay naturally went up. Now on average for those same commissions I make $12-15 per hour.
If you find that you cannot sell art for under minimum wage then instead of slaving away for very low rates of pay I strongly recommend researching ways to make your art better and more appealing--there are thousands of tutorials and books on drawing available. I don't recommend looking around at similar work and charging the same because so many people undercharge and that's how you end up burning out, that and maybe you don't work at the same rate they do.
I see, I don't think my art is good enough people would want to pay 30 dollars for it. (I understand what you're saying though and I know I could set the price range diffrent than you did.) Another problem is I get distracted easily so I'd have trouble keeping track of how long I actually worked on the drawing. So I'm not sure if I could take that route.
Another thing I don't like is that I'd rather tell them up front what the price range could be because they might not have the money they need to pay me with. Also I'd rather have them pay before so they don't just take the art and don't pay.
Also I'm leaning more in the points direction since I've never taken commissions before. Also I'm going towards points since my dad is thinking about setting me up a Paypal in the future. I'm wanting the points so I can get a Premium Membership.
I have tons of books and stuff, but all the books I can find are more detailed and intricate than I'm ready to do at the moment. I often will find references and stuff to glance at if needed and such, I've been working on improving my art a lot lately. Another reason I'm starting commission's is so I can get a new tablet since the one I have sucks, I've used my best friends tablet before and the art quality was a lot better since it has sensitivity and stuff like that.
With this route you should go in knowing on average how long things take. Getting distracted shouldn't stop you from being able to time yourself a couple times and seeing what your average is. I don't change it per commission, some take a little longer, some a little shorter but I know that for most badges say, I take about 2 hours of work. There will always be outliers but for every long badge there's a short one. If all of them are longer, well then clearly my average is off.