Steven addressed a lot of good points.
I coached at an affiliate for over a year and have rehabbed a few CF injuries in my current practice. I only have my weightlifters perform Olympic lifts now and that cured a lot of problems almost immediately. Instead, we utilize sandbag cleans, heavy kb swings, and tire flips for weighted hip extension.
My suggestions would be:
1. Plan out your programs such that the same exercises are consistently addressed at a variety of intensities to enhance both strength and muscular endurance. Pick a core of 3-6 exercises that you address EVERY week for at least a 2-3 month period.
2. Undulate intensity and volume on a weekly basis, incorporate low intensity workouts for your regulars at least one a week.
3. Be sure that your programming appropriately addresses all planes of movement, pushing/pulling, extension/flexion, anterior/posterior chain, and upper/lower body. This is harder to do than one might think. Especially when using weights that aren't heavy enough to require that one appropriately recruit the proper muscles. The posterior chain, in my experience, gets left out in the cold a lot as a lot of folks compensate with the quads.
4. Have an alternative "basics" workout available for every workout you program and do not bombard beginners with too many random exercises. It takes a while to develop proper recruitment patterns and coordination, especially in your average beginner.
5. Smart scaling: Scaling power cleans with a barbell to power cleans with PVC pipe is not an appropriate way to scale. Think about what the workout is supposed to challenge: Is it hip opening? Is it shoulder stability? Etc. There are many exercises that can accomplish the same goal while satisfying the need to be less complex.
6. Don't run the timer. People are naturally competitive. Challenges are fun to run every once in a while, but have your daily training lead up to a biweekly or monthly challenge. Sacrificing form for reps on a daily basis is the largest contributing factor to injuries, plateaus, and imbalances.
As a trainer/coach, it is most important that you keep your people injury free and able to function in a better capacity in their daily lives. Its easy to keep it fun and motivating, but also safe. Most folks just want to get better at something and have some sense of autonomy in what they are doing. Make the goal something other than time and you can accomplish that.