If you want to gain a rough idea of how much you should be looking to sell your coins for, then have a look for similar ones on eBay to see how much other owners are selling them for. On eBay you will be able to see how much they are going to for in a good condition and how much they are going for in mint condition. Usually, collectors coins that are in pretty good condition can rake in a decent amount of money for its owners as people can be prepared to pay a lot to finish off their collection.
Another factor that will affect how much they are worth is whether or not it is quite a commonly found coin or whether you own a rare one. The less well know they are then the more money you can expect to get.
There are also dozens of other websites out there that connect coin collectors together to talk about their hobby and trade together. They may usually have links from this website to coin valuation websites that can give you a really good idea on how much they are worth. These websites can also put you in contact with regular buyers and collectors who might be willing to strike a deal with you for your coin. As the price of collectable coins tends to fluctuate on a regular basis, knowing about a website like this could be quite invaluable and help you to find the best deal out there.