Diane, I'm now a director of coaching (yes, any chance to big note myself) and I often only have thirty seconds or so to squeeze in some advice to a team I don't know.
Here are some basic question-answer bullet points designed for junior teams mostly consisting of too-cool-for-school idiots. You basically put the question and let them answer it (usually they're wrong) then you supply them with the answer, allowing you to look all Obi Wan Kenobi and stuff.
1) What do we do when they've got the ball?
Mark players. Closest to the ball quickly closes down the opponent. Everyone else marks.
2) What do we do when WE'VE got the ball?
Find space. Lose your marker, make yourself available.
3) If you're the first tackler, is it your job to win the ball?
No. It's your job to close the player and stop their forward movement. Jockey them, attempt to win if possible, but force them into a bad pass so a #2 tackler can intercept.