How to buy a used car in the US

Occasionally, one of my friends wants to buy a used car in the US and I found myself repeating myself over and over so I figured it's more efficient to write down my experience instead of answering individual requests:

Steps:

1. Determine a budget
2. Determine a few make/model/year-range combinations
1. the purpose of this step is to constrain your search in next steps. This is important because comparing deals in the market is much harder when you are not constrained to a few such combinations. 
2. find out which make/model/year-range combinations satisfy the following constraints:
1. within your budget
2. available in the market (e.g. http://www.craigslist.org/)
3. have good specs (e.g. http://www.edmunds.com/)
3. generally speaking, Japanese makes have a good reputation of being reliable and cost-effective. American makes are usually cheaper but less reliable (their average expected lifetime is considerably shorter than that of Japanese cars). European makes (especially German) are also reliable but more costly to maintain.
4. if you have child(ren), I recommend getting a van (or an SUV). Other vehicle types are usually too small for your child(ren). 
5. given the (high) prices of gas in the US, an important detail is the average miles per gallon (MPG) for a given make/model/year.
3. Hunt for good deal(s)
1. best of all: try to find a trustworthy person in your local community who wants to sell his car (which has few problems).
2. decide whether you want to buy from a dealer or an owner. Dealers have to make money, so a (normal) dealer's price will be a few hundred dollars more expensive than a (normal) owner's price. However, you will be far less concerned about frauds if you buy your car from a trustworthy dealer. Imagine how anxious you would be when you want to finalize the deal with an owner you don't know, and give him/her a few thousand dollars!
3. http://www.craigslist.org/ is a good place to start looking. 
4. consider trustworthy local dealers (which are hard to find).
5. ask the seller if the car had any serious accidents or fails emission tests. 
6. ask the seller to give you the car's VIN number.
7. this is obvious, but it doesn't hurt to state it. Do not buy a car remotely from someone you don't know no matter how tempting the deal is. It is a fraud.
4. Check VIN
1. http://www.carfax.com/entry.cfx (this is a paid service. You can buy a bulk so that price per VIN lookup is cheaper). 
2. if the carfax report shows that the car had serious damage, failed several emission tests, is stolen ...etc, go to step 3.
5. Check at a mechanic
1. find a reasonably priced (less than $50) mechanic
2. ask the mechanic if the car has major mechanical or electrical problems. if yes, go to step 3.
3. if the mechanic approves of the car, and you like it, don't waste your time and money, and buy it.
4. in case of minor problems, ask the mechanic how much would it take to fix them, and use this information to negotiate the price with the seller.
6. Make necessary repairs and maintenance

--update: a friend asked me to add a warning that multiple names may be on the title. In that case, you have to get EACH of the owners to sign for you. Otherwise, the new title will have other names in addition to yours (legally, you won't own the car all by yourself).