You just keep them in your wallet. And I suggest to look at the project of that coin. If the project seems good one and with great potential, which you can know after looking at their roadmap;development;team;partnership, you can wait for their listing in bigger exchange. If the project looks dead or with no utility then probably there is no point in storing them. These days, I do also receive some coins i.e. on Tronlinkpro wallet in trx Blockchain, I leave them without noticing. Who knows if they pump or get listed?