A Simple Pre-Round Warm-Up for Junior Golfers

A five-minute routine that gets a young golfer's body and focus ready, without needing a full practice facility.
Move first, swing second
Before any club comes out, a couple of minutes of light movement - arm circles, gentle trunk twists, a few bodyweight squats - helps loosen up a young golfer who's likely been sitting in a car on the way to the course. This matters more for kids than it might seem, since children often go from stationary to full-effort swings with no transition.
Small swings before full swings
If there's time on a range or practice net, start with short, slow half-swings with a wedge before working up to full-speed shots with longer clubs. This gives a young golfer a chance to find rhythm and balance without immediately trying to hit the ball as far as possible, which is usually where early-round mishits come from.
Finish on the putting green
If the course has a practice putting green, a few minutes rolling putts of different lengths just before teeing off is one of the highest-value uses of warm-up time - it calibrates a young golfer's feel for that day's green speed, which can vary a lot between courses and even between mornings and afternoons on the same course.