Submerge Yourself In Ideas

As you get ideas about what genres you want to tap into, and the look and feel of your band; come up with what instruments/talents you need and how many.

Although it's nice to have a lot of talents and more instruments, remember... the more members you have, the smaller your chances get of having something successful.

You have to coordinate your practice times with different people living different lives that may revolve around work, family, school, etc. - you name it.

The more people there are, the bigger chance for clashes in the band.  You don't need clones of yourself, yet not having like-minded people, or at least people with similar goals may present problems.

Sometimes less is more, no need to overdo it.  Doing that could result in CHAOS, and unless you are good at getting people to listen and have a lot of talent to back it up, I would stay away from having too many members.  As long as you have the basis of a good band, more talents can be added on as you continue your journey.