A Good Start

The first day is coming up fast and I've gone over the first five priorities I'll need to cover in the first practices, my priorities for putting in the offense, and outlined my practice plan for the first day. I've even reflected on what it will be like handing out the equipment. That is a good start, but I'm thinking about having a good start when those 25-30 eager, energetic faces are in front of me waiting for direction. They won't wait long either before they basically begin being typical middle school boys.
The cliche would be "setting the tone." I think establish authority would be more accurate. You establish authority by being organized, having a plan, and following through. Being organized is knowing where everything is that you will need for the practice, lesson, season etc. Having a plan is knowing when to use what you will need. Following through is doing what you say you're going to do. If you tell the kids you're going to get a new piece of equipment, you better deliver. If you say you'll have them do "extra work" in practice for being late, you better make sure they do the "extra work." Extra work is often equated to running and sometimes it should, but try to be more creative than that.
Following through might be the most important of the three. They (and the "they" can be parents as well as the kids) are always watching your reactions, and some (unfortunately, you can include parents in the "some" too) will test to see if you really mean it. With discipline, I don't recommend warnings, especially early in the school year/season. Calmly, unemotionally follow through with what you said would happen if a rule is violated. However, effective organization and planning will cut down, but not eliminate, the need for discipline. There's no doubt in my mind that kids want structure, despite what they may be showing outwardly. Its anecdotal evidence, but I've heard kids complain about teachers or coaches who give a freer rein, as much as they complain about those who they perceive as stricter. I know kids don't want to have their time wasted either. If you do an activity that's meant to kill time, don't kid yourself, they will know. They won't like it, and they will act out because of it.
That first day you have those 25-30 eager, energetic faces in front of you, be organized, have a plan, and follow through. Then you'll have the confidence to speak with a clear, strong voice giving specific directions for activities that have direct relevance to what you and the kids want to accomplish. And if the need for flexibility arises, I've found it easier to be flexible when a detailed plan is already in place.