It's important to be organized when doing commissions. You need to make sure you know what you're drawing for each person and if you've gotten payment from them. It's also important to figure out how many you can take at once, and that usually depends on how much time you can spend doing the art. People prefer a fast turnaround time, but obviously that cannot always happen, and people are usually understanding about that. Pricing is important too. You should make sure that what you're charging is making it worth your time to do commissions.

moshi-moshi :D haha hello
first of all. i want to thank you for the watch

i just read your journal :D and i think the best way to start a commission is to have an internet bank account, like paypal :D
you can make one for free :D its not really hard :D

second, you must start with the pricing
i went to your twitter and gallery.... judging from your drawing skill, you have great talent :D so I'll leave it to you when it comes to pricing

third, you can start letting people know you are doing commissions :D
you can do that from journals, or maybe post a picture so that people will understand better :D

thats what i did last year :D so give it a try
I love your art :D so you'll do fine
i follow your twitter too man i love the way you draw anatomy :D theyre hot