Make sure you take a test drive. Not every car suits every person, even the Versa.
Arrange your financing in advance. If your credit is super, you might be able to qualify for the low rate offered by NIMC, but don't count on it. You don't want to be pressured into financing through the dealer at a higher rate than you otherwise could have gotten if you can't get credit from NIMC.
Do some shopping around and mental preparation. Dealing with car dealerships is no joke. There are some nice ones out there that want your business and want to build customer loyalty, but there are some real stinkers out there that just want to take your money.
A web site you should look into:
http://www.carbuyingtips.com
Also, most bookstores have at least a couple of books on buying cars, most of which are pretty decent.
A few hours of research can save you a lot of money.