A great way to avoid not getting paid for your work is to deal with a reliable bounty manager and even better, work on coins already listed on a high quality exchange. I have been using KuCoinPlay and it has both those attributes. I have averaged $200 in earnings each month.
If, for example, I am interested in a project, then I try to study it carefully. Basically, I do those projects that are already traded on the exchange or those that have set a goal, and also announced the listing date. And of course, if the manager is known with a good reputation.