The best way is to use Sales History and start searching for the card. If the card has been verified by our Research Team it will show up on Ladder and you'll get more in-depth analytics about the card including all-time sales history, graphs, growth over time, population reports, etc.
When you search a card on Sales History you'll see the value of the sale and the date it occurred and you'll also see the CL Value.
If you're interested in the value of cards in your collection you can also head over to Collection and add your card. There you will be guided to help determine the value of your card using the same methods as CL Value.