For me, the whitepaper is just a paper which tells their business idea. It was written and can be changed. Look out for the team members, are they willing to reveal their true identity or are the images they claim to be them really represents them?
Are there some well-known personalities involved? Look out for advisers, do they really represent them or just added them there.
For instance, if a project adds Vitalik as an adviser, don't jump into conclusion and invest with them. Look on his twitter walls, he will definitely tweet about them.