I say this with a real heart to all artists, but that is a foolish line of questions.
Really. I have been there. I even did those myself. But look at it from the side of a potential buyer.
1: Would you even commission me?
Can you imagine if a doctor were to say that? If I were to open an office would you even come to me? That makes the doctor feel like a failure. Like he has so little faith in his ability to do his job he is afraid to do it. So he has to ask a thousand people IF he were to open an office would ANYONE come? Would you? Or would you want a doctor who just opens it and does his job and believes in his ability to treat you?
Same with an artist. You sound like you have no faith in your ability. If you do not believe in it, how can anyone else?
If you want to offer commissions, offer them. Do not ask if you should, announce you have.
2: How much would you pay?
This is an awful question. Let's imagine for a moment you go to a car dealer. The salesman comes out and says they have a brand new Aston Martin, a car that is like $200,000 or more. But the salesman is new and is not sure what the car is worth and asks you what you think is a fair price?
Would you REALLY say, "This is a $200,000 car, plus markups." Would you say that to ensure the salesman made his commission and could pay for his debts and fees? Or would you see a chance to get an amazing car for dirt cheap? "Well, this car is a dull color, and look, not a lot of flash. So...maybe it's worth $2.000. But I could pay you $1,200 if you could add a few things."
While a few may be truthful, most would use this chance to get something as close to free as possible. There would even be a few who would tell this salesman that the car is not really worth anything, but he still wanted it, so he should get it free and he would tell his friends to come here for more cars.
Do you see how foolish it is to ask? You will only be told to do it free or very cheap, because human nature makes us try to get the most we can for the least amount.
Something I learned early when I published my own comics, NO ONE will tell you that you matter. YOU have to tell them you matter. Same with commissions. No one will tell you when your art has worth. You have to tell them it has worth. What in your art has worth?
1: Your time.
It takes you a few hours or a few days or weeks. All that time working on the art is time away from friends, loved ones, hobbies, entertainment, practice, even sleep. Does the loss of all that have no value?
2: Your material.
I assume you use something to create art. Paper, pencils, lens, inks, paint, canvas, markers, computer, tablet, stylus, software etc. You had to pay for that material, right? That had worth when you bought it, should it not have value to the one buying your work on it?
3: Your skill.
If you are up to the level someone wants your art, then you probably have spent thousands of hours on your art getting here. Like a surgeon, the more he does the better he is, the more specialized he is, the more he can charge because his SKILL puts him in demand.
4: Your community.
Look out for your fellow artist. If you come out and offer dirt cheap art, you are undercutting all other artists. Cheap commissioners will see an artist charging $200 for a commission and you, who think you have no worth, charge $5. You make the artist trying to make a living look greedy. The commissioner comes back to the first artist and says, "I can get the same thing here for $5!" Do you think he will buy yours? Not always. He will use it to try to talk the first artist's prices down. If that fails, then maybe he will come back to you. But he will offer less than $5. It is better to work free than cheap. But free is a waste for you, unless you are doing free art for a dear friend, family, or for a charity.
So, what should you do? Look at your art and be honest, how good is it? There are 3 levels.
1: Beginner. You have a decent grasp on basic art. But you have more to learn. Then you should charge no less than $20 for a full color single character with a basic background.
2: Mid level. You have a solid grasp on art. But you are not quite to the 'pro' level yet. Then you should charge no less than $40 for a full color single character with a basic background.
3: Advanced. You have a strong grasp on art. But you have not gone pro. Then you should charge no less than $60 for a full color single character with a basic background.
That is just a very basic note. You are the one who sets your price. If you think your art is worth more or less, you can slide it. And if you are a pro artist, you should charge more, because now your name and place adds value.
If you HONESTLY cannot justify charging that much for your art then maybe you are not ready yet. Commissions are not to be done lightly. This is a business. If you want to do them, treat it as such. For your benefit and the art community.
So if you are ready for this what should you do?
1: Create a price list. This is your prices, cover as much as you can, but do not make it too complex. Keep it clear and simple. If the buyer has to do mental gymnastics to get a price on their request they will walk away.
2: Announce everywhere you can that you are doing it. Keep it simple. Say it in a proud way, with confidence and pride.
3: Be ready to wait. Really. When you begin to offer commissions there will not be a crowd of buyers running up to you, waving money. There will be stretches of time where no one wants a commission. Why? Because of the people doing them free or dirt cheap. (See?) And sometimes people do not have the money. So wait. What can you do to speed it up? Offer a sale from time to time. Limit the number of slots. And promote it.
4: Promote! Go to clubs, groups, etc and announce you are going commissions. People LOVE their Original Characters drawn. Let them know you are doing just that.
5: Get out. Set up at the local mall or shopping center (after you get approval) and do sketches. Go to a theater where they are showing a comic book, sci-fi, horror, any cult follow level movie and do sketches to people who just saw the film.
So there we go. Sorry this became more long winded than I planned. But I want all artists to succeed. And only by standing together and making sure we are getting what we deserve, can we do that. So go forth and do art!
UPDATE: If you do use points for your commissions, please use this to see what those points are really worth.