compactness theorem proof

rainwyz0706

An expression of the compactness theorem for sets of sentences is that: let T be a set of sentences in L. Then T has a model iff every finite subset of T has a model.
Could anyone give me some hints how to prove this?
The first direction is straightforward: every model of T is a model of every subset of T. But what about the opposite direction? Any help is appreciated!

JSuarez

My advice would be to not try to reinvent the wheel, and study the proofs given in any logic textbook.