There is a lot of great advice on this thread:
I completely agree with Audiofeil's advice on visual ratings. Even with great sellers, you can get the occasional dud that looks great.
If you are trying to buy more collectible, i.e. expensive records, find a few sellers you trust and establish a good relationship with them. When you get the occasional dud, a good seller will graciously allow a return.
Box sets, especially classical sets, are often rarely played and usually offer great value.
Certain record labels offer consistently great sonics, others not so great. It pays to do a little research before bidding.
Know whether or not you are getting a first pressing (which typically sound better and are more valuable). It pays to recognize the labels, producers, etc.
A good record cleaner is a must.
Good luck. Finding great old records is the one of the most enjoyable parts of the hobby.
