Once you've worked out the general type of car you want and you've got a feel for the budget, it's time to whittle the many possible to a few probable cars.
Use the Compare tool in New Cars to compare the features of several vehicles at once. For example, if you're looking at sedans, check the box to the left of two or more car photographs and then click the Compare button at the top of the listings.
You can also use the "Similar vehicles more..." link at the bottom of each individual car listing. This will bring up vehicles with similar specifications to the one you are looking at.
Once you've got a list of potential cars, do some additional research into those particular models. Car Survey.Org is a not-for-profit global website which allows owners to post reviews of their own cars. The Press carries a comprehensive set of test drives for most recent car models. Consumer carries useful reliability information about most mainstream makes and models.