Formal:
* Avez-vous du papier? (Do you have paper?)
Informal:
* Tu as du papier? (Do you have paper?)
* Y a du papier? (Is there any paper?)
If you're asking specifically for paper to write on:
* Avez-vous du papier pour écrire? (Do you have paper to write on?)
* Tu as du papier pour écrire? (Do you have paper to write on?)
The best choice depends on who you're talking to and how formal the situation is.