During my trevelling in Asia, I have been checking and using these reservation portals:
Booking.com (usually, booking without paying in advance. Sometime guarancy by card)
Agoda.com (always paying in advance with your card, no cancellation, but the same hostel can be cheaper then in other portals)
Hostelworld.com (partially paying by your card)
Others (Hostelbookers.com; Tripadvisor.com).
Actually, I have Android apps of these portals with my account, so I can easilly do reservation in my tablet.
When you search, sort by cheapest and choose by reviews, and also look of photos of hostels. Be carefull, when you arrive in late night to check if hostel is open 24 hours. Do reservation, and then, notice the name, address and GPS coordinates of the hostel (very practical, when you put to your offline maps).
You can do reservation (ussually, in my case), or just notice the address of hostel. It is depend of the hostels and country. Sometime, when you make reservation through portal, it is cheaper then reservation personally (happent to me in Singapore, Tokyo and China), and sometime, opposite (Nepal, India). But it is not a rule.
In some countries (like India), not all hostels are in booking portals. So, you can just ask people in the place or search in the internet or inspire by guide books (check, if hostel still exists).
If you want to stay with local person for free, try Couchsurfing.com.
Or rent just a room in people’s house or flat (for longer time), try Airbnb.com.
=== Knaper ===