On the trail, don't pass up Lake Overlook, it provides an awesome view of the lake, benches are there, to relax, and there are some great photo ops.
The lake is clean, but people fish there, so swimming is not recommended :)
No parking fees. Toilets available.
Take the Glenn Highway north. Immediately after crossing the Knik River Bridge, the exit will be on the right, then, just follow the signs.