I read this tip at frets.com. Take you favorite guitar along when shopping for a new one. Instruments can sound much different in different environments and taking an instrument that you are familiar with will give you a reference point in which to compare. I have never thought of doing that, but it makes a lot of sense. Or, at least, when you get the field narrowed down to a few, then take your best ax in to compare.
I would also suggest cleaning it up beforehand and putting on new strings. Before you make the final decision on a purchase, you might want to have someone else play the guitars while you stand in front where your audience might be and do a comparison. They can sound a bit different from that perspective than when you are playing them.
Of course, if you can get a 90-day buyer's remorse no-questions-asked money-back guarantee, that's good, too.
Hydroman52