Do your homework before you check in. Go to Hostelworld.com or Hostels.com to read reviews by other travelers and see current rankings, which tend to be reliable. Smaller hostels tend to have a stronger communal feel, though you're in closer quarters with that community, while bigger hostels (100-200 capacity) can feel anonymous, which works if you're on business or already traveling with friends.
For a complete listing of hostels in the U.S., check out Jim Williams' well-established "The Hostel Handbook for the U.S.A. & Canada," updated yearly ($4 plus shipping and handling, http://www.hostelhandbook.com).
Many hostels offer low-cost communal dinners, which vary from cafeteria-quality dishes to outdoor barbecues to the surprisingly gourmet. At Pacific Tradewinds, Sunday night dinner consisted of a full roast chicken, spicy Italian sausage, roasted corn, mashed potatoes and a colorful salad of mixed greens, beets, green beans, tomatoes and bell peppers — the best $5 hostel dinner I've had.
Most hostels have a communal kitchen; boiling up some pasta and veggies is a great way to break the ice with other travelers. Check activity boards for local farmers markets and grocery store locations.
Hostels are known for freebies — check to see what dinner outings or events are going on when you're there. Breakfast is usually included in the rate (make-your-own pancakes are ubiquitous), so are coffee and tea.
Banana Bungalow locations offer free airport shuttle pickup from the Los Angeles and San Diego airports and free parking at their facilities. Check hostel websites for most up-to-date bus and public transport schedules, and for walking directions from bus and shuttle stops.