Eisenach is known for the Wartburg, one of Germany's oldest (existing) and most visited castles. The Rennsteig, a long distance hiking path (170 kilometer), is also very nearby the city. Eisenach is also the homebase of the hitchhiking club "Club of Roam - Autostop! e.V. ", organising the Tramprennen.
The complete situation around Eisenach (Thuringia) has changed a lot during the years 2009 and 2011. A new motorway bypass for the A4/E40 has been built. The old A4 is now the new B7/B19/B 88 but not leading back to the autobahn A4 in eastern direction any more. Some stretches have completely been dismantled. Older maps might not be showing the present situation correctly.
From East (A4): Ask the driver if he can bring you a bit closer to Eisenach to the old Autobahn (), it will be just 5 min longer for him to take this way because from there it is very easy to head on West as you see on the map. And you are now very close to the entrance of Eisenach. You can reach the city centre from there in an half-hour-walk.
Or: Just get out of the car at the exit "Eisenach-Ost" and try to catch a lift to Eisenach directly at the exit.
From West (A4): Ask the driver either to let you out at the exit Eisenach West and hope for a ride to Eisenach or ask the driver to bring you a bit closer to Eisenach to the old Autobahn (), it will be just 5 min longer for him to take this way because it he goes just over the hill East back to the A4, Eisenach Ost as you see on the map. And you are now a bit closer to the city center. Either you take the bus from Marktkauf or Eisenach Nord in direction Hauptbahnhof or you have an half-hour-walk.
West: To reach LOMO Autohof Eisenach from the city centre of Eisenach you can take bus number 5 to "Karlskuppe" until "Obere Kassler straße" and hitchhike directly at the bus stop or some metres behind. Use a sign "A4" or "Creuzburg" (next village). You can ask the driver to bring you to the petrol station.
East: Take the bus number 5 to "Karlskuppe" and hop off at the last station. Once you are there, ask people at the petrol station near the McDonalds if they are going to the A4. Most do and they just need to drop you at the roundabout close to the Autobahn. From there you can walk to "Am Marktrasen" and continue on the street "An der Autobahn" to reach Rasthaus Eisenach Nord. There will be signs that trespassing is forbidden but the area is just riddled with abandoned factories and nobody cares if you walk through. You can also easily reach the other side from there by just climbing up the stairs.
Other option: Take bus number 1 to the 'Marktkauf' supermarket and shopping mall. Get off there and walk 10 minutes uphill to one of the many traffic lights on 'Mühlhäuser Straße'. It should not take more than minutes to find a (commuting) driver that can bring you to the 'LOMO Autohof' on A4. Build a cardboard sign indicating 'A4 ' (or 'Autohof') on it. The Autohof is on one side of the autobahn situated for both directions, once you have reached it you do not need to change sides (east/west).
Two important facts: Don't be worried about the name "Autohof", its a proper petrol station and its quite easy to hitchhike there! And you can hitchhike two both directions from one side, but there are two gas stations! On on the upper level to the west and one on the other level to east.
From the Eisenach LOMO Autohof you should be able to reach Erfurt (40 minutes), Jena (60 minutes) or Dresden (two hours and 30 minutes) in eastward direction as well as Kassel (70 minutes) or Frankfurt (one hour and 50 minutes) and gas station "Kirchheimer Dreieck" (45 minutes, where you can switch two A7 direction Hamburg) in westward direction.