Techniques for proving bounds on integrality gap in LP(SDP) A reference to techniques for proving that the size of an integrality gap is bounded by some expression for a particular LP(or SDP, but less important) is needed. Also it would be nice to have a reference to a place where techniques for minimizing integrality gaps are described. I am new in the area of integrality gaps, which looks rather huge, so description of classical results is more preferable than that of something hot.
This is somewhat heavy machinery for what you want, but there's been a large body of work on techniques for designing ever more refined LPs (SDPs) that get closer and closer to the desired integer program. A good reference that reviews these approaches is by Monique Laurent: A comparison of the Sherali-Adams, Lovasz-Schrijver and Laserre Relaxations for 0-1 programming. 

Apart from that, I am not aware of a single good source of references: I assume you've at least perused the relevant chapters in Vijay Vazirani's book ?