Watching a few weather forecasts is the key. Usually if winds are less than 15mph, the ride will be okay. Anything more, and things can get bumpy. (I second the NOAA marine weather and buoy websites to get a sense for wind and wave heights.)
The good thing about Lake Michigan, at least the area you'll be crossing, is that it's deep. The only possible collision is a log or another boat, but paying attention should eliminate such a boo-boo.
I trust you'll have a GPS. If that decides to not work half-way through, make sure your compass is calibrated properly so you can manually steer to the correct heading. Even though you'll see land, you also want to be headed towards the harbor entrance and not 10 miles south/north of it.
If you're not using an autopilot, it's a good idea to show a crew member how to steer the compass heading so you can take a break. Even 5 minutes to stand up and not be focusing on the compass needle will do wonders to recharge your ability to concentrate.
I've crossed Lake Michigan more times than I can count, and it's one of the most enjoyable experiences in the right weather conditions with properly functioning electronics. Cocktails are nice as well, but be sure to bring plenty of bottled water in case something doesn't go as planned, and be sure to know where safety items are in case you need to quickly ditch.