My go-to spiel:
- Have captains shake hands.
- Statement about sportsmanship and how they need to police their teammates.
- Ask them to help us retrieve the ball on incomplete passes.
- Tell them we'll give them their options on penalties.
- Ask if they have any questions.
- Ask visitor for coin toss selection, go through coin toss mechanics.
Depending on the level of youth football you're talking about, I might skip 4 and 5 (and go straight to the coach for penalty enforcement selections when necessary).