Seriously. Virtually every time a potential client chose a different contractor over us because of price, we eventually received a call from them expressing their regret and disappointment for not going with us. Don't put yourself in that situation! You will get what you pay for.
Once you think you've chosen the right company for the job, be sure to scrutinize the contract. Ask questions about anything you're not sure about, and make sure they give clear answers. The last thing you want is additional charges after you thought you've made your final payment.
Good luck out there!