There are tons of threads in this forum with people asking opinions on whether a particular car is worth buying or not based simply on sales price, options, and mileage. Obviously, nobody can really make that determination without actually inspecting the car. Especially over the internet!
So if you are not extremely knowledgeable about used cars, how can you make an informed buying decision about whether a particular used car is worth buying or not, or whether the asking price is appropriate? By knowing what to look for in a thorough
used car pre purchase inspection (PPI). Knowing what to check (and how to check for it) can go a long way to helping you avoid a bad buying decision. Also, unless you really are a true expert, it's a good idea to defer to a professional who knows what to look for in addition to making your own inspection. Many places have qualified and ASE certified mechanics who can provide this service for you for anywhere form $69-$200 depending on the service. If a car passes your own personal muster, it may be well worth that amount of money to get a second experienced professional opinion on the car you are considering.
Here is a series of excellent videos on how to check out the basics of a used car for yourself even if you are not particularly car savvy. I will stress once again, it is still a good idea to pay for a professional PPI unless you are 100% sure that the car checks out or if you rule it out from your own persona inspection. Also attached is an example of a PPI I had performed on a dirt cheap used M5 that I was considering buying. The inspection showed me that IMO it wasn't even worth the 4 hour drive up to Dallas to check it out in person; I passed.
A note to those of you with short attention spans who like to be spoon fed: The 4 videos run just over an hour in length. However they are fairly comprehensive and could possibly help you make a better decision buying the second largest purchase of most peoples' lives. If that's too much of your time feel free to skip them and go it alone on your own knowledge.