Trout like it cold, so in winter time they can be at any depth, as long as there is good oxygen.
If the lake has good forage, with shallow structure, the fish will use it, especially if the water gets to hot in summer for them to use the structure.
For Rainbows, I like to find a nice large flat, with sand and gravel.
I use tip ups, so I can try different depths. Keep track of the depth that you get fish to hit at. You'd be surprised how it stays pretty consistent from year to year.
Always remember to run a high line.
One year I limited out, fishing 6 feet down in 30 feet of water.
If you can, talk with people who fish the lake - see if they can give you a general area to start fishing.
Hope this helps,
Wiener
