It depends on whether they're doing a 506(b) or a 506(c) offering. The difference being that the latter can be publicly advertised, whereas the former doesn't allow any public solicitation of investments.
In the former case, you can take people at their words (they just declare that they are, and how they are an accredited investor in a statement).
In the latter case, you must verify via a statement from a licensed professional (e.g. their CPA) or via their bank.
In the former case, you can take people at their words (they just declare that they are, and how they are an accredited investor in a statement).
In the latter case, you must verify via a statement from a licensed professional (e.g. their CPA) or via their bank.