Depending on your budget, Amsterdam has a great range of hostels from the amazing to the repulsive.
The absolute cheapest hostels are also generally the most filthy and nasty to stay at. They do if you literally need a bed, and don't particularly care what it's like. These are probably around €15 a night to stay at. I wouldn't bother having been there and done it.
Next up are the slightly more respectable hostels, which are kept clean and don't cost so much more to stay in - closer to €20-25 for a bed in a shared dorm. Flying Pig and Bulldog are generally recommended for decent quality levels of service and cleanliness!
For an alternative, there are a few houseboat hostels which are generally located in the docks close to Centraal station. The ones I've been in have been clean, tidy and run by friendly people. They can cost a few euros more than other hostels, but provide a unique place to base yourself whilst in the city.
Best thing to do is search hostels sites for rooms in your budget, and then cross reference with TripAdvisor ratings and reviews. Bear in mind though, most people only make it to TripAdvisor when they have a real issue with a place they have stayed, so take everything with a mild pinch of salt.
Hope this helps a little. Maybe I should make an Amsterdam hub!