Anonymous team or team with weak experience is one of them.

As expert said "Understanding who is on the team behind a blockchain project is perhaps the most important step in your due diligence. Even if the premise of the venture and the addressable market seem attractive, one of the biggest determinants of a venture’s success is the makeup of the team behind it".

It is often a red flag if the team behind an ICO does not have any named full-time developers. Additional caution should be taken if none of the leadership team has any domain knowledge in the specific vertical.

When looking at a team and verifying their experience, platforms like Twitter and LinkedIn are useful. However, it’s important to note that they are not infallible, as profiles can be faked. If members of the team claim prior association with universities or companies, double-checking with reputable third-party sources (e.g. a university newspaper or the company website) can provide the facts.

ICOs often list their advisors on their websites. You should also verify whether the advisors are legitimate.