If you come by commercial plane, then one of the nearest airports is Düsseldorf (DUS). From there you can take a S-Bahn to Düsseldorf and then a regio express or ICE to Hagen, then a local train to Lüdenscheid and then finally a bus to Herscheid. Easy, eh?!
Alternatively, you can fly in in your own sports plane to the local airport Herscheid-Hüinghausen.
Herscheid lies between Luedenscheid (end of Dortmund-Hagen-Lüdenscheid line) and Plettenberg (on the Siegen-Essen line) so you can actually arrive at either train station. Plettenberg may be easier because bus no. 54 which takes you to Herscheid leaves from in front of the station whereas in Luedenscheid (the other end of bus no. 54) the station is far from the station and hard to find.
If you really want to come by public transport, then you can take bus no. 54 from either Lüdenscheid or Plettenberg. To both of these towns you can take the train. But of course it's more convenient if a friend picks you up.
Herscheid lies only 6 km from the motorway A45 (Sauerlandline)to Dortmund or Frankfurt a.M. It's 12 km to Lüdenscheid, the nearest bigger city.
Take the A45 autobahn to Lüdenscheid and look very careful at the map where to get off and then to take the right turn to Herscheid.
This is very small place, you can walk around, but there is also a horse farm here so, you can take the horse and ride into the fields and forests around.