I've been keeping notes of my favorite campsites at the Indiana State Park campgrounds that we visit. Here are my recommendations...
Once you prepare for the rugged trails, you can appreciate the beauty of Clifty Falls. My favorite trail was #2 which takes you straight up the creek. The campground was smaller than I expected, but had good, level sites. They did not have a camp store, just firewood sales at entrance. The best site is #24 backing up to woods and having a large side lot. However, I noticed they created a new site, #23, which would also be good if they allow reservations. #40 is my second choice, followed by #9 and #11. If you go with a group, I recommend 55 & 56, 69 & 70.
Spring Mill was my favorite Indiana State Park campground so far. The campground & park are spacious and allow for lots of running, walking and bike riding. In addition, we were able to enjoy a hayride around the campground! The outside lots of the VIP area (116-122 ), the grassy areas of (67, 68, 70 & 71) are great camping sites, as well as #83 (my favorite!), 81, 49, 55, 165, 167 &187. If going with a group, I recommend 90 & 100 or 111, 133, 129 & 128. Seems like you can't go wrong at Spring Mill!
Turkey Run is my second favorite campground, thus far. My favorite sites were #7, 156, 157, 81, 38, and 65. If you are looking for more wooded, check out 175, 183 or 223 & 224 (together with a group). 268 and 269 offered some grass and space, but may have road noise from the adjacent highway.