Is there anything like a good signature campaign again? As long as you find one that is accepting your rank and you are OK with the pay, then I do not see any reason why you should not join. You are only gicing your signature space out for rent, and that is the way I see it. However, if you are looking at bounty signature campaigns, then you might just have to dig in the project to know if it would be worth investing so you do not end up wasting some months on a scam. Digging involves how feasible the project is, does it sound like a scam, can it work, does it have a good team? And so on. See yourself like an investor who is giving his time and space for the project. However, if the project pays in BTC, then you have nothing to lose.
This is all just you need to look out for in a signature campaign. You are only doing a job for someone and you end up getting paid for it, so looking for a good signature campaign is totally based on your preference.
If it is a bounty campaign, then the decision is left for you to know if it is a project worth working for since your reward would be in stake and you would not want to end up with a scam coin at the end or just working for a project that would not even survive the ICO.
If your payment is in BTC which usually it is every week, then you have nothing to worry about as long as you are comfortable with what is given to you.