After reading their whitepaper then ask yourself these questions:
1. Does the document make sense to you? (Did you get a picture of the whole idea they are talking about?)
2. Is project going to provide any real solution to any problem? (scam projects usually provide vague solutions which normally does not point out the blockchain aspect in it)
3. Is the document having original contents (scam projects usually copy people's work)
4. How old is their official website (most scam projects usually have new websites)
5. What has the team done already towards the project.(scam projects usually do not have any detailed roadmap)
6. Check the team's profile on linkedIn and also their number of connections. (fake ones usually have low and no real connections.)
7. Check the token distribution. Is there equity and equality? (the scam ones usually allocate higher percentages to the team)
8. Did they give any abnormal price speculations? (i joined one bounty(Crestonium) who promised 3 times profit within 6 months else they are going to refund investors monies back to them. They ended up being a scam)

No matter how vigilant you are, you can still get scammed but at least, you can reduce the risk of being scammed. Enjoy your day