Once you have decided what cars you wish to focus your search one, it's a good idea to contact the dealership by phone before shopping in person. This can give you some sense of the business atmosphere you will be dealing with later, through the buying or leasing process. You can also find a salesperson suited to your needs or demographic (if you just show up, most lots assign the next salesperson on the list to you, regardless of suitability to you), and can establish a rapport with the salesperson. Call and ask if the car you're looking for, in the color and right options, is actually on the lot.
If you are shopping via the Internet, you can contact the Internet manager through e-mail message or by telephone. You can also send multiple dealer requests to narrow your search based on availability, price and tone of responses. If you called the Internet department, tell the salesperson that you want to set up a test drive. Let them know that you won't be buying right away, but that you will buy there if you decide to purchase this particular make and model, and if they can offer the vehicle at a fair price.
Keep in mind that if you deal with the standard salesperson, he or she will try to start the negotiations at a high price with the expectation of being negotiated down. However, the Internet manager will often quote you a "rock-bottom" price as soon as negotiations begin. A few minutes taken to set up an appointment with the Internet manager can save you both time and money
The goal of a test drive is to experience - as closely as possible - your typical driving conditions after purchase. If you commute, drive the car in both stop-and-go traffic and at freeway speeds. If you frequently drive into the mountains, try to find some steep grades to climb (up and down slopes). Drive over bumps, take tight corners at aggressive (but not dangerous) speeds and test the brakes in a safe location, such as a deserted parking lot. Get in and out of the car several times and be sure to sit in the backseat, especially if you plan on carrying passengers. Check the size and handling of the back door or trunk. Evaluate what it will be like to live with this car for a number of years.
Don't pay attention to the salesperson's pitch, and don't drive with the radio on (it can hide mechanical problems) because you can evaluate that sitting in the lot. Rely on your intuition, especially if you are uneasy about this car. A vehicle purchase decision is the second biggest investment most people make (after their home) to undertake without total confidence.
Following the test drive, you should leave the car lot. You will test drive other types of cars at other dealerships around the same time. If you do your various test-drives in one morning or afternoon, you help uncover minor differences, subtle conveniences or inconveniences, which will lead to a more educated purchase decision.
Generally, a salesperson you met through the Internet is more mellow than the assigned car lot salesman, and shouldn't pressure you to buy on the spot. Just remind them you still have other cars to drive and you can't make a decision yet. Most good salespeople will respect that, and you probably won't be coming back to deal with them if they didn't.