Let’s start a game used bat thread.

[JoeDfan]

Like card collecting, rule number 1 is:
If it looks too good to be true, that is because it is!

A general rule of thumb that I use, and this doesn't always apply: If the bat has the inches marked on the knob, I generally consider it a retail bat; unless there is compelling evidence to the contrary.

Also, do not confuse signed bats, which might have a PSA or JSA sticker on them, with game used bats, which might have a PSA or Mears sticker on them.

If you want to collect bats, I suggest get the book, and then start small, with a few "known" bats that have PSA or Mears letters with them. Louisville Sluggers are a great way to start out, because the books will help you ID the gamers pretty quick.
There are also a couple of other great books on bats that are must haves.

If you like it, after a while, you will start taking chances on a few more of the bigger fish.

One thing that I watch out for is that I can totally talk myself into believing any bat is a gamer; so I often get an objective opinion if I can before doing anything crazy.