Hostels probably won't offer you the same amenities you'd get at a hotel. While virtually every hostel will provide guests with sheets, a blanket, and a pillow, you might not have access to a towel and soap, for example. Research what you'll need to bring with you ahead of your trip, or be prepared to buy certain items when you get there.
Other amenities you may want to confirm are laundry service, printing, city maps, postal service, and bike rentals.