What skills are needed to sustain a research group?
I try to only work with people who are capable of excelling in all the skills needed to perform and write up high-quality research.
That's not to say that some of them (particularly students) won't need training in those skills in order to excel, of course. But I definitely don't believe in having 1 guy who only collects data, 1 who only analyzes data, and 1 who only writes (or some such scheme). If you pursue such a scheme, you may be crippling people. They'll likely have a hard time in their next job, when nobody holds their hand through the other parts.
Setting goals: As a PI, you need some skills on top of the obvious (like writing grants). One important skill involves setting goals. You need to be able to set reasonable and attainable (but not necessarily easy) short-term goals for your group. At the same time, you need to be able to clearly articulate the overarching long-term, big-picture goals of your research. Good goal setting will help you attract capable researchers to your group.
Some team-related skills:
Interviewing. You have to build your own team, and that team has to fit together very well. Given that your research group will likely be small and that your work can be measured in years, a few mistakes here can be very costly to your ability to produce. Be sure you know who you're bringing in, whether you can work with them, and whether when they can work with the rest of your group.
Delegation. There's an art to knowing what to delegate and what to do yourself. This will vary from researcher to researcher, and from one graduate student/postdoc/lab technician to the next. Make sure you don't give someone more than they can handle, and make sure that each person has enough to keep them busy.