I would say that most entrepreneurs do almost no reference checks or at least do them very informally. Don’t let that be you. Most VC’s will happily supply you with a list of CEO contacts of the people who will speak to you about working with them. Don’t be afraid to (politely and respectfully) ask for this. In fact, they will think better of you because you’re demonstrating that you’re the kind of thorough person that they wanted to invest money into in the first place. Don’t stop there.