We put in from the boat ramp in Shepherdstown. Four of us in a canoe. The river was shallow in many places, and there were quite a few small rapids that were difficult to negotiate; in some places, we had to get out and pull the canoe over the rocks. But that's all part of the fun.
We took out at Dargan's Bend (north of Harpers Ferry), where we left a car.
Including a stop for lunch, the whole trip was about five-six hours.
There is some parking at the boat ramp in Shepherdstown - but no restroom or latrine.
There is more parking at Dargan Bend, and two latrines.
Any map can give you directions to Shepherdstown, WV. When you come into town, turn south on West German Street (230) - a left turn if you're coming across the Route 34 bridge from Maryland. Then turn left on North Princess Street - there is a sign that says, "Public Stream Access." The street dead-ends at the boat ramp.
To get to Dargan Bend from Maryland, take US 340 west from Fredericksburg. Just before the bridge that crosses into WVa, you'll see a sign for a left turn at Keep Tryst Road, which takes you to Sandy Hook Road. From Keep Tryst, turn left on Sandy Hook. It goes under Route 340 and up the east side of the Potomac -- turns into Harpers Ferry Road. Stay on Harpers Ferry Road. After you pass Pleasantville Rd., look for a road that goes off to the left - BEFORE you pass the Manidokan Camp and Retreat Center. The road is called Back Road, but there is no sign. Follow it down to where you see the road into the boat ramp.
Dargan Bend boat ramp described at www.riverexplorer.com/details.php4?id=810 - but their directions are not quite accurate.