Without knowing a lot of details, the first thing I’d do is figure out what the forage base in the lake is. That will give you a huge leg up on finding muskies. If it’s shad based, you may be looking at a lot of open water stuff over the creek channel and along the sides of the channel on points and inside turns at certain times of the year. If it’s more of a perch/minnow/sucker/panfish deal, you’ll do a lot more rooting around in the timber. Forage will also sort of give you some ideas on presentation – color patterns and lure size. A good place to start with that kind of research is calling the local DNR fisheries guys and picking their brain about the lake a little. They’re usually really helpful. Another good idea is to see if there are a lot of bass fishermen on the lake. Bass guys stumble into muskies quite a bit on some lakes, and they may be able to provide some info. Have found some awfully good muskie spots over the years by listening to bass heads whine about getting bit off all the time on certain spots.
Another thing to see if you can find out is whether or not the lake stratifies during the summer. If it does, and you can figure out what depth the thermocline develops at, you can eliminate everything deeper than the thermocline. No sense fishing the bottom of the creek channel in 20 feet if the thermocline’s at 12 feet.
You’re right on things changing from season to season. It’ll probably vary widely. But, the usual rules of thumb still apply – look for warmer water early, and follow the food. I know on some of the Illinois lakes, guys do extremely well up in the timber early, either casting spinnerbaits, or even trolling Believers through the stumps. Believers bounce off things pretty good, and with a short line (30 feet) you can control where they run pretty well. If it’s a shad based lake, walk the dog topwaters and rattle trap type baits can be very productive.
Hope this helps.