At first, catch the idea: sell piecemeal. Let’s say, if you have 100 coins and they are x2 or more from their initial value, sell 50%. Then wait and watch for a rate change, if it has a strong down trend, sell the rest. But if price grows, sell 50% from the rest 50% and watch for changes again. It’s called diversification and it helps to minimize risks and to maximize possible profit. Also, listen to wise advice and do research. Don’t sell coins in which you believe and get rid of ones which seem trashy. As for specific places where to sell, check CoinMarketCap’s page of your currency. There is the list of all available exchanges. I’d suggest to sell it on cex.io after reviewing its features here newbie deactivated link:https://www.katiewager.org/cexio-review [nonactive] if you want to get fiat, or on Binance if you keep funds in BTC/ETH. Remember that market is volatile and your profit may turn into loss in a day or even hour.