Campbell Hill is extremely easy to get to as it is basically in a parking lot of a school campus! It will be hard to tell you are at 1550 feet in elevation. You'll have a nice bench to sit on at the site as well. The trip from the state capital of Columbus to the state highpoint is just an hour drive.
From I-70 West take exit 93 to merge onto I-270 North towards Cleveland. Take exit 17B off I-270 to merge onto US-33 headed west. Take the OH-540 East exit for Sandusky Ave. A half mile down the roadyou will find a school on the right side of the road. This is your destination.
Campbell Hill is open Monday through Friday 6:30am-10:00pm. It is also open on Saturdays all year round from 6:30am - 3:00pm. Try to go during these hours. Remember it is a school so don't get caught creeping around at night or on Sundays trying to get the highpoint.
Also, Hoosier Hill, the highpoint of Indiana is only 2 hours away so highpointers will be able to easily get both these in a day.