How do you ask your mom if you can go to homecoming?

Ask her nicely. Figure out why she would be hesitant. Are your grades bad? Does she not like the guy you would be going with? Does she not have the money to spend on a dress? Address the issue, for example, if she doesn't have the money to spend on a dress, tell her you will find a way to pay for all of it, or half of it, or you can borrow or make one. Homecoming is a right of passage. Have fun! And, don't turn down the nerdy, skinny senior that asks you because 10 years later, you will run into him at a hip bar on the night of the Marine's birthday and he will be in well filled out dress blue uniform and looking super hot and you will have gotten what you deserved...not even so much as a hi from him. (true story, happened to me)