The value of a card depends on a number of factors: Scarcity (how many copies of the card were produced), who is depicted on the card (a 1959 Topps Mickey Mantle is many times more valuable than a 1959 Topps Wayne Terwilliger), and even where you're trying to sell the card (an Ichiro card will probably sell better in Seattle than in Baltimore).

But given two of the same card -same set, same player - the biggest consideration is the condition of the card. You will have to gain some knowledge of card grading and condition. The condition depends on a number of factors, some more important, perhaps, than others. These factors include:

Attribute	What to look for
Corners	Are they sharp and not "dinged"?
Edges	Are they smooth and straight?
Color	Are the colors bright? Are there color spots (usually caused by printing imperfections)? Color is usually more of a problem on older cards.
Surface	Are there chips, scratches or creases?
Centering	Is the image well-centered on the card? Again this is usually more of a problem on older cards, where the card may be cut so off-centered that it includes a recognizable part of another card.

Cards are graded on a scale ranging from "Poor" (absolutely terrible condition) to "Mint" (perfect as far as you can tell). See the "Articles" main page for some card grading guidelines. A magnifying glass is pretty much a necessity for serious grading.

Various professional card-grading services exist, where you can send the card and they will grade it and encapsulate it in a sealed holder with the grade marked on it. Of course, they charge a fee. PSA, Beckett and SGC are well-known and respected professional graders.

As a beginning collector you will quickly become acquainted with Beckett. They provide the generally accepted values for cards. You can find the values online at their website or in several magazines that they publish. The website price guide generally costs about $6 per sport per month, but I think it's worth it because all of the cards are there and it's (relatively) easy to find the ones you're looking for. It can be hard to find a price in the magazine because not all of the cards are there, you have to know whether the player is a "semi star", an "unlisted star", etc., and you have to deal with "multipliers".

Don't accept the Beckett prices as gospel. As far as I'm concerned they are suggested prices. They provide a starting point from which everyone can work. But when someone talks about the "book value" of a card, he or she probably means the Beckett book value.

As you start to accumulate cards, you will soon realize that you need some way to keep track of what you have, mainly for three reasons. You want to be able to find a particular card at any time, you may want to avoid buying another of a card that you already have, and you want to know what cards you're missing. You can do this with purchased software, such as "The Card Collector" from CPP, Inc. Such software will usually provide market values for your cards.

You can, of course, do it yourself with an Excel spreadsheet, for example. This will not automatically give you market values, but that may not be important to you (you can always look up those values).

As your collection grows, you need some orderly way to store it and/or display it. I use BCWsupplies myself to supply my storage boxes. I've also bought display cases from Pennzoni Display Company. You can display your cards in three-ring binders using nine-pocket plastic pages. I do NOT recommend putting your valuable cards in binders, however. Put them at least into hard sleeves if not screw-down holders.

There are long-term and short-term investments. If you had pulled a Jeremy Lin rookie card or autograph card late last year (2011) you may have been able to sell it for thousands or tens of thousands of real US dollars in February or March. If you elected to hold on to that card in expectation that the price would continue up or at least hold that value for some time, then I'm afraid you're going to be disappointed. The 1985 Topps Mark McGwire card in 1998 was selling for hundreds of dollars. Now you can probably find one for $10 or less. Same with the Jose Canseco rookie cards from 1986 that sold for several hundred dollars in the late 1980s and can now be had for a few dollars. Sadly, there are lots of such examples.

On the other hand, a 1952 Topps Mickey Mantle card that you might have bought 30 years ago for just a few dollars could today be worth hundreds of thousands of dollars, depending, of course, on condition. As is the case with many things, "if only we'd known then what we know now". Many cards of high value, such as Derek Jeter or Cal Ripken Jr rookie cards, can be expected to maintain their value or go up. Many players' cards get a bump when they make a Hall of Fame or (sadly) die, or even when they do something spectacular - throw a no-hitter, for example, or star in a World Series. Those bumps are usually short-lived.

In my opinion, I don't think you as an individual collector are going to get rich buying and selling sports cards today. If you work hard at it you can maybe make somewhat of a living. But the good news is this: if something happened to me today, I think my wife could generally get back at least as much money out of my cards as I originally put into them. So considering how much enjoyment I get out of the hobby, I guess I'm satisfied that it's a good investment!

I need to spend a few words talking about non-sport cards. As I mentioned earlier, there is seemingly no end to the variety of cards that you might collect. Personally, I have a bunch of Harry Potter cards since I'm a big fan of those books and movies. I also have a small (but growing) collection of auto and memorabilia cards from movie stars. There's a professional poker player or two in my collection. One of my oldest possessions is a card featuring George Harrison from the early 1960s Beatles cards. You may have to work a little harder to find these cards, but they are out there and they may be just what you're looking for.

And in conclusion, let me say: There's no right way or wrong to collect cards. There's just your way. Collect whatever you like. Put as much or as little money into it as you like. Don't let others tell you what's right or wrong. I don't apologize for my Harry Potter cards any more than I do for my Elgin Baylor autograph or my 1933 Goudey Mel Ott. If you're having fun then that's all that matters!