There’s probably nothing more important than who you associate with in your life. This is absolutely the case when it comes to whom you hire or partner with. Invest a lot of time up front getting to know your key employees and partners, when possible try to see them in action for several years before formalizing your relationship with them. This may not always be possible of course. When it’s not, talk to as many references as possible and try to have the candidate spend time with you in both work and social settings. Try to ensure that at least one or two of those get-togethers has some stress involved (golf is a good place to encounter stress, for example), to see how that person reacts under pressure. When interviewing, be sure to use real life scenarios if possible, and make sure you introduce a time factor or some other element(s) that make the situation stressful. In my experience, under stress is where a person’s “true colors” are most likely to emerge. In the absence of stress and time pressure, you are likely to get fooled by a great acting job..
I think a key characteristic I look for in others is the ability to take negative scenarios or bad situations and be able to communicate about them with a positive slant… either through analysis, solutions, suggestions, ideas etc. This ensures that the problems in business transend personality and bias, and it helps to prevent the development of negative & no-can-do attitudes within a group.