For how to know which tokens are not on the exchange how? and how to sell the token how? honestly I have never sold my token once
Tokens that are not in exchange shouldn't be your problem but whether your tokens are listed. You can know this at least by visiting
https://coinmarketcap.com. Type your token on the search space to see if it there or not. If you see it listed, you can know the price by also clicking on the market space down on the same page and you also see the exchange that it is listed.