its very difficult to answer .all depend on your choice and situations. if you are in money urgency you will have to sold them once recived. but if you dont have such a situation i recomend you to study about the project before selling. if it looks like a good project advice you to hold it for long time. if its not a good project vest thing is sell it once listed on a major exchanges.usually majority of project listing on decentralize projects like idex and etherdelts.that not make big impact on price.wait untill it hit on a major centralize exchangers like bitrex,polonix,binance or ect.also if market is on a major depression like these days strongly adviced to hold your all coins once market/ bitcoin get stabilized or rised.