Every week, we see people who have found their old hockey card collection from their childhood, joining a Facebook group asking about the value of their cards. It's not uncommon that they believe they've just struck gold, and are about to make big money. Here is a list of some of the things to keep in mind.

Staggering print runs
In the 1990s, hobby interest was at a peak. An enormous amount of hockey cards were produced to meet demand. As a result, base cards from this era carries almost no value. This is also true for many inserts and parallels. Chances are, this will be the absolute bulk of your old collection.

Condition of your cards
When you were a kid, you most likely didn't store your cards in penny sleeves and top loaders. There is a good chance you shoved them in your pocket and took them to school, or had them all in one big pile in a shoebox. For your cards to carry value, they generally need to be in very good condition. This means impeccable edges, sharp corners and no scratches to the cards surface. 

There are still rare cards, even from the 90s
While the above statements are true, there were rare cards made, also in the 90s. If you have one of them, in good condition, they will have value. Some insert sets are sought after (like the Premier Padmen) and some super star players have collectors all over the world (like Jagr, Lemiuex and Gretzky).

Modern Cards
The most commonly used way to determine the value of a modern card in the hobby, is to find comparable sales of that card, or of other similar cards. A site such as 130point will let you scroll through the last 90 days sales history from E-bay. For a card that is printed in many copies and is regular traded, such as a Young Guns card from the latest flagship release, you will have no problem finding comparable sales of that exact card. For more rare cards, such as a /25 card that may only sell very rarely, you may struggle to find other sales. In that case it's advisable to compare your card to other similar cards. For example the same /25 parallel from the same product, but from other comparable players. Or of /25 cards of the same player, from other comparable parallels.

Be aware though - the ebay sales history on 130point lists all sales, including those that were never paid for. Especially for more expensive cards this means you may be looking at inaccurate sales data, so don't trust it blindly. There are other tools to use for this as well (ebay's sales tool terrapeak is to my knowledge the only tool that filters out non-paid ebay sales), and there are more sites than E-bay that sell cards.