My favorite, fee-free site to check sales across auction houses is 130point.com/cards. Be sure to use the /cards page; the /sales page just shows eBay sales.

Searching sold listings on eBay also works great for casual research. If needed, I also recommend trying Mavin.io for even older sales.

• Identify your card and deteremine it's condition. Cards with heavy creases are generally considered to be in Poor condition. There's a large range between Fair and Mint condition; review SGC's guidelines to learn more.
  
  
• If graded, it's easier to search for your exact card. When doing so, sort by Price, lowest first, and filter to Buy It Now listings only. This will help you identify the cheapest available example and establish a ceiling value for your card, as it's unlikely a buyer would pay more for your card than what it's readily available for elsewhere.
  
  
• Use parenthesis and commas to require the results to have just one of the listed words. This is great for searching for graded cards from all the major companies in one search.
  • ex. Instead of searching PSA T206 Cobb then SGC T206 Cobb, just search once for (PSA,SGC,BVG,CSG) T206 Cobb
• Use negative keywords to filter out undesired results
  • ex. T206 Cobb -(reprint,reprints,reproduction,rp,topps,replica,postcard,dover,promo,renata,galasso,1988)
    
    
• Get creative when desperate. If the last directly comparable example sold 5 years ago, have values of the player’s other cards changed since then? What about other cards from that same set?

• Consider the date of the last comp, the total graded population, and the frequency of sales. If it’s a card without many sales, is it because not many graded examples exist? Or is the card common with no demand?
  
  
• Always check currently available Buy It Now listings on eBay when pricing cards. If there’s one currently listed for $280, it doesn’t matter if the last sale was $350.
  
  
• You’ve heard it before: buy the card, not the grade. Not all cards of the same grade are equal. Eye appeal matters a lot for high end cards. Consider the centering, surface and corners of historical sales and active listings that appear to be outliers.

Finally, know your pricing strategy.

Are you looking to move the card asap and want fast cash? Or are you happy to hold the card and only want to sell for a certain amount?

When possible, know your bottom dollar price before starting a sales negotiation. It’ll keep things simpler, and you’ll be happy if you’re able to sell it for more. There’s no one right answer as to how and when to buy, sell or trade, just decide what’s right for you.

Founder of T206Cards.com, passionate dealer of vintage collectibles.