This is a question that is asked quite often, there are in fact entire books dedicated to this very question. Be that as it may, in my opinion I think the answer is quite simple and not nearly as multidimensional as some would lead you to believe. Not to say that there are not multiple things you need to have right, I am just saying that it is not as many things as some would have you believe.
It is only an opinion as will be any answer you get but be that as it may, mine would be to do just four things religiously.
1. Pay them what they are actually worth or someone else will
2. When they talk, you listen
3. When they give advice, you take it
4. Give them the ability to make the right decision without having to get constant approval from you or anyone. You have stated that you are looking for people smarter and better than you so this should not be anything for you to be concerned about.
I hope you find these people and that you can keep them. It is tough to do as everyone else is looking for them as well.