When you come on motorway D5 from Pilsen use EXIT 128 (Nová Hospoda, Bor, Tachov). Next way is very good marked as to Tachov.
If you come on motorway D5 from Rozvadov use EXIT 136 (Svatá Kateřina, Tachov). Next way on Tachov is very good marked.
When you use northern way the easiest is road number 21 via Marien Bad and on first crossroad in Planá use road number 198 on Tachov
Click into the map picture for more details.