Welcome to the boards Nita, as with the advice above, list what you have in the relevent forum area, NRL, AFL, Cricket etc. List with as much detail and some photo's / scans and members can give you advice on worth. Take that advice on board along with a search of eBay completed listings and you will have a good idea what price to set. Also describe the condition as accurately as you can, to hard core collectors condition is everything and can greatly affect the price.
Remember that if you sell on here as a member, you will be required to send your cards first as new members with less than 10 feedback points are required to send first here at OCT.