The first step is to carefully go through your collection and identify cards from the most popular players, especially stars from past eras who are now retired. Focus on legendary names like Babe Ruth, Mickey Mantle, Willie Mays, Hank Aaron, Jackie Robinson, and other all-time greats from the early 1900s up through the 1980s-1990s. Their vintage cards tend to hold the most value since they were printed decades ago and capture players’ early careers.

You’ll also want to look for star performers from recent decades like Ken Griffey Jr., Cal Ripken Jr., Barry Bonds, Mark McGwire, Sammy Sosa, Alex Rodriguez, and others from the late 1980s through early 2000s. Their rookie cards or cards from milestone seasons could potentially be worth something depending on condition and scarcity. Less common parallel or autographed variations of modern star cards may carry higher values as well.

Next, assess the condition and grade of any potentially valuable cards. Things like corners, edges, surface scratches or flaws all impact a card’s condition. Near Mint or Mint cards will hold much more value than ones that are well-worn or damaged. Have valuable cards professionally graded if possible by a recognized service like PSA, BGS, or SGC. Graded high-number cards can significantly increase in price.

Do research on recent sales of comparable cards to get an estimate on value. Sites like eBay, COMC, or PWCC let you search “sold” listings to see what similar cards in the same condition have actually been selling for. Pay attention to trends over time as well, as certain cards may be hotter and demanding higher prices at different points.

You’ll also want to consider rarity factors like serial numbers, parallels, autographs, patches that make a standard card more unique. These specialty variants can be worth significantly more than a basic base version. Do your homework on production quantities and how scarce a specific parallel, serial number, or autographed card may be.

Once you have an idea of values, assess your goals. Are you wanting to sell individual high-value cards? Maybe look to assemble a complete set and sell that as one lot. Or consider holding cards long-term as investments that could appreciate further down the road. Properly storing your collection in protective holders is important to maintain condition if investing long-term.

When considering selling, weigh options like direct to another collector, group auctions on eBay, or consigning through a professional sports auction house. Auction houses have reach to a wider collector base but will take a sizable commission percentage. Always get appraisals from multiple experts before making investment or collectibles-based financial decisions as well.

Do your research on player pedigree, production numbers, condition, comparables, and current market trends/demands to best gauge if your baseball cards hold value. High-grade, rare pieces from all-time legends usuallyoffer the highest return potential – especially when accurately graded/encapsulated. With some homework, you may discover hidden gems worth protecting and possibly realizing profits down the road.