Well, I don't know what people do. But I myself will always consider these:
- See the manager bounty rank and its track record
- Analyze the ICO if legit or not, trusted or not
- Count the token allocation to the signature campaign and make it into dollars
- See the participation lists whether those are many or few participants (better to choose less)
- Check the rule and regulation, I will choose the signature with approximately 15 posts per week