Normally it is more advisable to sell your coin collection to another collector, because he will have the same interest, and he will pay you the best price for your collection. There will be no intermediary between you and the other collector. Firstly, you need to search for another collector who is willing to purchase your collection of coin at a reasonable price. Before meeting any buyer it is advisable that you should pack your collection of coins properly, so that it is safe from theft and damage at the time they are being viewed.
Security is a great problem that you may face when you are selling it to a dealer. Will you be able to find the dealer again? If you are announcing it to the public, or you are publishing an advertisement in the newspaper that you have a coin collection, you are just inviting the thieves to you. At the time of examining how much can you trust the person you need to stay close, otherwise later on you may find that some of your precious coins or bank notes from your collection are missing.
Another possible problem you may go through is that there is a possibility that the buyer you get is not willing to buy the whole collection you have prepared. He may want to select certain best pieces from your collection. If you are willing, you can go ahead with the deal. If you are not, then you need to search for another buyer with the same interest.