I prefer to park on Locust Pt. Rd lot, this puts you in between Hartshorne and Huber. If you are making the trip its worth it to visit both parks, Huber is a smaller version of Hartshorne. This is my standard loop out of Locust Pt, I hit a lot of it in both directions because its fun and do a clock wise loop at rocky pt., I'd recommend going ccw, for less climbing. In Huber I do a counter clockwise loop because I like to.
https://connect.garmin.com/modern/activity/2271970592
If you don't garmin, here is a map of Hartshorne. Clay Pit Run/Right Laurel Ridge/Right on Cuesta Ridge Rd/Right on Grand Tour about 1.5 mile then left to climb up hill/straight across rd to Rocky Pt. trail, this makes a big loop with a nice view of the Navasink on your right as well as extended views of the Atlantic. Eventually you will come to a road with a parking lot. Refer to map and take the road heading toward command loop, make the right onto grand tour and this will put you on the trail you came in on, follow it out in reverse of the way you came in. You are now probably totally confused and taking time to read and following my directions will cause zero flow out on trails. If so, just ride your bike for 2hrs and try to find someone there willing to give you a tour.
http://co.monmouth.nj.us/documents/130/hartshorne_aug17.pdf