Long but bear with me:
Let me first say I don't know why more people don't locate and negotiate their car purchases through the internet more often! Luckily, I've never done the traditional go-to-the-dealership-and-stay-all-day deal and proud of it.

Bought my first (and second) cars--both Mazda3s--via internet sales.
I think internet sales is an especially great method for anyone who has a very particular combination of specs that may be hard to find.
I also like the fact that you can kind of pace the process and have time to do extra research as needed.
[quote author=icspots link=topic=136788.msg2957551#msg2957551 date=1235455473]
www.carbuyingtips.com
[/quote]
Agreed. I found this site very helpful when buying my cars.
The most helpful part of this site (to me) is the offer spreadsheet. Plug in the numbers and it calculates everything for you so you know what a "good" offer on the car is. I use edmunds.com to get all the invoice costs, destination fee, and incentive info. I also use Edmunds just to see what the TMV happens to be. (I use other sites as well but this is the main one.)
Once I've
determined what a good *out-the-door* offer would be using the spreadsheet, I make sure it's not over TMV for whatever reason. Then I click around on dealers' sites and sites like
AutoTrader.com to get an idea of what's likely to be in stock.
Next, I
draft the email I plan to send to the internet salesmen in my area. In it I state when I plan to buy, what I am looking for, and ask if they have anything that meets these options. I note that I have contacted other dealers in the area with the same info. I also ask them to provide the specs on the vehicle(s) (including non-std options and mileage) and their asking price. (Ideally, they'll eventually send you the digital window sticker for the car.)
So, a few things to keep in mind at this point:
- By emailing multiple dealers, they all start looking for the same vehicle and may be less likely to trade vehicles since they know someone's looking for it. Depending on the situation, this can be good or bad for you but I won't get into this.
- Dealers usually have sister dealerships with inventories that may have your ideal vehicle. I've never done the walk-in thing but I doubt a dealer is as likely to offer you a car from another lot as a walk-in, especially since these vehicles are sometimes out-of-state. (But I can't say for sure.)
- Some internet sales people won't get back to you. I've decided this is either because they think they do not have a car for you or they have no interest in your business for whatever reason. Their loss.
- Sometimes the salesperson wouldn't completely provide all the info your are requesting. Usually it is because they do not want to spent time provide all the details on a car you may or may not be interested in. Understandable. Play it by ear. Just make sure you try to get as much information as possible throughout the process.
After emailing, wait and see what responses you get. If someone presents 3 cars and I'm only interested in 1, I tend to reply explaining that I am most interested in car B but not in cars A and C for XYZ reasons. I find this helps the salesman identify your priorities. I also find that they are more likely to go back and do another search with this feedback and come back to you with more cars. And this 2nd or 3rd search will turn up a car even better than car B you thought you had to settle for.
During this time, I take my best prospect and go back to my spreadsheet as needed to factor in (or out) changes from my original specs.
But DO NOT MAKE AN OFFER ON A CAR UNTIL YOU KNOW ITS THE ONE YOU WANT. Obviously, the salesperson is gonna want you to commit ASAP but do not make an offer until you know for sure. I try to make sure they provide me with the VIN of the car and its mileage before I make an offer.
Once you have pinpointed the car you want, reply to the dealer, let them know which vehicle you are interested in, and request their asking price. I've found it's usually a reasonable price (before TTL and fees).
Reply with your out-the-door offer and make sure to note that it is your out-the-door offer for XYZ car. I also include that my offer is obviously conditional on a physical inspection and drive of the car.
Sometimes the dealer has found a car from out-of-state (the case both times for me). Be sure to ask if the car is being transported from another location and, if so, request it be transported by flatbed. I failed to consider this the 1st time (and my first car may have been driven in instead of flat-bedded but I'll never know). Oh, and the transport is an unofficial part of your OTD price. It should not be added separately.
Once the car's ready, go to the dealership, inspect the car, fill out the paperwork, and drive off happy!
Now, to give you an idea of how I've fared:
In Dec 06, I got a manual 07 MZ3s sport with side air bags for $18200 OTD. I can't remember what TMV was at the time but my MSRP was just over $20k.
This month I'm replacing that car with an 09 (not by choice). I was offered a manual 09 MZ3s sport for ~$2000 under invoice. I probably could have offered less for it but was a decent offer, I wanted the car (a manual MZ3s is hard to find to begin with around here), and I didn't want to haggle over a few hundred bucks. I try to leave the dealer a bit of profit.
Hope that helps. *Definitely* check out
carbuyingtips.com as icspots suggested. This site might also help:
www.realcartips.com.
Good luck!