Warmups
The players will not arrive at the same time. You will need to be at practice a few minutes early. The early arrivals give you an opportunity to give some one-on-one instruction.
Have each of the players jog fifty yards or so to get their blood flowing. Then they should spend 4-5 minutes stretching legs, arms, neck and torso. Now they are ready to begin throwing.
As soon as they are ready to throw you should provide someone for them to throw with. Ideally, they will throw with someone of roughly equal ability or with a coach. The pitchers should warm up with each other or a catcher.
Have a coach watching their throwing. Warmups should involve work on throwing form. If the players are just tossing the ball casually or using bad throwing technique, ask them to do it right.
Pitchers should be practicing their changeups to emphasize a full throwing motion. This is one of the best times for practicing the changeup since you want a big motion at first in warming up and the changeup should be thrown with the full fastball motion.
As the early arrivals finish warming up move them into individual drills that do not require much space. Pepper games, bunting, pick-off moves, steal starts, and underhand toss drills are examples of things one or two players together can practice without using much space. If a drill requires a lot of space, you will not be able to supervise all the players since they will be too far apart.
Lectures
As a former college professor I love to lecture. Coaches in general love to hear themselves talk. The boys are not playing baseball just to hear us talk. Therefore, try to have each lecture occur while the players are doing something. Listening to a lecture about pitching is much more fun if you are pitching at the time. While you lecture about batting give each player a bat to swing.
Since the best way to learn is by doing and the worst way to learn is by hearing about something, have the players do what you are trying to teach while you show them and tell them about it.
Drills
Individual drills have no place in your practice unless you have a lot of assistant coaches. Practices are the only place the players can work on the “teamwork” aspects of baseball. It is good to teach the players drills they can do alone but then go on to other things and let them do the individual drills at home.
Base running requires a lot of players to practice well and involves many baseball skills. You can work on pitching, pickoff moves, throwing, rundowns, steals, covering bases, backing up bases, sliding, and tag techniques during base running practice. Plus the players enjoy doing it.
Instead of ordinary infield practice with one player at a time catching a grounder and throwing it to first, you can use base runners who wait at home for the sound of the bat hitting the ball. Then, if they are safe, they stay on base and provide the opportunity for force outs, line drive double plays, and base running on hits practice. As the one hitting the ball, you can control what kind of situations you want to practice. This way you can keep up to a dozen players involved, doing baseball things, having a good time, and working on an array of baseball skills. You can have the nine fielders (the pitcher is a fielder once the pitch is thrown) all involved plus the players running the bases.
Pitching practice should be part of every practice. This requires game situation pitching with lots of base runners. If your pitchers have dealt with aggressive base runners in practice a lot they will not be overcome by aggressive base runners in games. This practice for your pitchers is also an opportunity for your batters to practice hitting. They should get regular at bats with three strikes only just like in a game. The usual batting practice pitching which involves slow “easy-to-hit” throws by a coach does not help anyone much. The batters will not see that kind of pitching in a game so why practice hitting it?
Outfield drills should involve fly balls with runners on and reacting to hits with runners on. Just hitting fly balls to the outfielders will not help them much since they need to do that on their own. Working on making low throws to the infield and backing up bases is much more useful. Also, since they are probably your weakest players, work on base running and hitting by these players can help your team run production noticeably.
Use of Assistants
What you can do with assistants depends on their quality. Some assistants are only good for helping carry the equipment bag. Some could take over the team without missing a beat. If you have good assistants, use them to increase the coaching the players get. Pitchers benefit by 10-15 minutes of individual attention per practice. It also helps if during pitching/batting drills (see above) the batter is being coached. During warmups, the coaches should be working on the players throwing motions.
A good assistant should be consulted and given responsibilities. This keeps them happy and gets more work from them. Whatever they do best in coaching, give them responsibility for that. You should take whatever the assistants are not so good at. You will need more than one coach working on the pitchers. Be sure that you are all “on the same page” in pitching technique.
Sequence of Events
Warm-ups must begin the practice. Drills in small groups and pitcher/catcher work are next. The practice should end with a chance to apply, in game situations, the material you have covered in the drills. You need to reinforce the material covered and put it in the context in which they will need to remember it.