Five suggestions:
1. Read the Consumers Report annual auto issue (April) for ratings and reliability of vehicles of interest to you. Either buy a copy or visit a library.
2. Then go to the Edmunds web site to look at their reviews and get dealer invoice pricing, holdback info plus current factory incentive info.
http://www.edmunds.com/
3. With some info in hand test drive your top choices.
4. Once a make/model is nailed down and you are ready to buy, and only then, and armed with Edmunds pricing, talk $$ with dealers asking them what they need to get over invoice. Make the trade-in value a separate issue, in reality you will only get wholesale value. If convenient do this at more than one dealer.
5. As many have noted, say no to the hard sell for extended warranties.