The most interesting trails are in the southern section of the park. I’d suggest parking at the main beach: from there it’s easy to access the trails, check out the campsites for a future visit, but mostly to be able to get in the water after your hike!
I did a three-mile loop (as you can see in the bottom right photo) combining the Central Sands Trail, the Turkey Hollow Trail and the Partridge Trail Loop and thus was able to enjoy some open areas, some woodsy sections and some parts along Castle Rock Lake.
And to see the DNR’s map of all the trails, click here.