You need to know the type of tokens that you have. Their are many tokens on coinmarketcap and you can use coinmarketcap to locate which exchange that your tokens are listed on. There you can exchange your coins/tokens to either bitcoin or Etherum and convert to fiat thereafter
Well we also have to know what token we hold, and this depends on where your token has this for sale. There are many exchanges and markets, not all tokens exist in all markets. If you have found a market that sells token owned then it is better to sell in a large market. it is usually very crowded and of course the opportunities are sold higher than in the small market.