The first step is to carefully evaluate the condition of each card. Baseball cards can vary widely in value depending on their condition. The main factors that determine a card’s condition are centered around the card stock itself and any flaws/imperfections present on the front or back of the card.

For baseball cards graded from the 1950s through the 1980s, conditions are generally evaluated on a scale from Poor to Mint. Poor condition means the card is very worn and tattered with corners rounded and edges frayed. Fair condition means more significant wear but corners still pointy and no ripps/tears. Good condition is pointy corners but worn edges and possible small creases. Very Good has sharper corners but some wear and possible light creasing. Near Mint is sharp corners and edges with only very minimal wear and no creases. Mint is a pristine card that looks uncirited.

Starting in the 1990s, professional grading services like PSA and Beckett added numerical grades that give a more precise condition assessment, on a scale of 1 to 10. A 1 is in poor/damaged condition while a 10 is a completely flawless and pristine card. Condition grades of 7 and above are considered “investment grade” for serious card collectors.

Once you’ve evaluated the condition of each card, the next step is to identify attributes that could impact the cards’ values. Key attributes include the player, year, team, whether it’s a rookie card, autograph, numbered parallel, refractor, etc. These special versions can exponentially increase a card’s worth compared to a standard base card.

Now you’ll want to conduct online research to get a sense of estimated market values for each particular card based on similar recently sold listings. The three main sites used for this are eBay, PWCCMarketplace.com, and AuctionHouses.com which aggregate sales data from major auction houses like Heritage, SCP, and Goldin. Be sure to filter search results by card condition to find appropriate comps (completed sales of comparable cards).

Taking into account conditions and special attributes, you’ll want to note a range of estimated values – usually a low end for sale in standard/lower grade and high end for top grades. For example, a 1998 Derek Jeter base rookie card may have a value range of $50-150 depending on its specific grade/condition.

It’s also important to consider the timeframe – what similar cards have sold for recently (within last 6 months) vs what they may have sold for a year or two ago. Prices can fluctuate significantly depending on the hotness of that player or team at a given time.

The final step if wanting to sell the cards is determining the appropriate marketplace – whether it be on eBay yourself, using a consignment model through an LCS (local card shop), sending high value cards to a major auction house, or selling the entire collection at once to an online company. Each option has pros/cons around potential sale prices, time commitment and convenience factors.

Proper research upfront will allow you to best understand approximate values for your cards and strategize the most advantageous selling approach. Only with a detailed analysis of conditions, attributes, recent sales comps, and market options can you determine optimal prices to offer your baseball cards for sale at today’s prevailing market values. Let me know if any part of the process needs further explanation!