[drcy]

A lot of it is a matter of fashion. Some sets just become popular at certain times, some formerly obscure and some mainstream.

Also, think out of the box, as it were. If you're saying "what baseball card is a good investment," you're already limiting your choices and picking from an already popular area. Be wary of today's hot areas and fads. The best investments are quality and rare items no one is paying attention to right now.

I always say the best investment is what you buy today and sell tomorrow for a profit.

My last two cents of investing advice is remember that you're return is based on what you pay. Many people pick a card (So and so's rookie cards) they think will increase, but overpay for it. If you overpay, you can lose money on a card that increases in book value. If you buy at a bargain, you can make a return on a card that doesn't. A card isn't an investment. It's the amount of money that you put into the card that is the investment. It may be the same card from the same issue in the same grade (etc), but one person buying it for $100 and another for $150 are different investments. Or as Benjamin Franklin said, a penny saved is a penny return on your investment.