If you have a hand held vacuum with a motorized brush roll attachment...you've got the best tool for vacuuming your stairs. Second best on the list is a lightweight stick vacuum cleaner. As a last resort, use your attachments on your upright or canister vacuum. Handling bulky full-sized vacuum cleaners on the stairs isn't fun, but it can be done. Luckily, your stairs don't need to be vacuumed daily.
How Often to Vacuum Stairs:
Try to vacuum the high traffic parts of your stairs once or twice a week. Once a month do a more in-depth cleaning of the corners and edges as well.