I've worked in startups for 18 years or so and two of the key lessons on hiring I've winkled out are:
1. always hire people who are cleverer than you (I have an advantage with this one).
2. always hire people who can do things that you can't i.e. hire specialists.

I'm a generalist. I can do lots of things badly so mostly I'm delighted with the skills and personal qualities of the people I work with. The issue though is when you really, really don't understand the role that you are hiring for.

A couple of things I've learn on this. Never outsource the problem - never ask someone else to make the decision. It's yours, make it.

Also, however, because you don't know what to expect of your prospective hire, you have to hire someone that you can genuinely trust. By which I mean 'Trust their judgment, not just trust them not to make off with the cutlery'.

That can be difficult but fortunately that is exactly what most good people want in a working role so you can get great people if that's what you are offering.