One of your first stops should be Manasquan Reservoir Visitor Center. Here, you'll be able to orient yourself and pick up some great ideas before you set out exploring.
You'll have sightseeing choices galore when spending time in Howell. Manasquan Reservoir Visitor Center is a great place to kick off here, but there are loads of other worthy places to consider. Wall Township Speedway, Allaire State Park, and Woodlake Country Club are not far from the tourist information center and will fill in your day nicely.