I've never been through the locks between Lake Huron and Lake Superior, but I am a weekly user of the locks between Lake Washington and Puget Sound in Seattle. So I thought I'd touch on a few obvious, but important things to remember:
1. Make sure you have enough fuel! Trust me on this.
2. Make sure you have adequate lines, (at least two 60 foot lines with at least 12" eye splices, not hand-tied eyes). Be ready to switch lines quickly from port to starboard, as you will not know which side until you're in the locks. Always present the spliced end to the dock.
3. Listen to the lock workers instructions carefully, they will bark instructions and warnings that you'll need to take heed of.
4. Prior to entering, hang lots of easily adjustable bumpers on both sides.
5. Be prepared for strong currents, when the gates open and close, (upwards of six knots).
6. If you're instructed to raft onto another boat, adjust bumpers accordingly and hand them the eye end of the line, so you are in control of the tie off and then they can easily cast you off when instructed.
7. When casting off to leave the locks, always cast off the bow line first.
8. Kids and pets should not be on deck, as falling overboard in the locks is a really bad thing.
Good luck and have fun!