Hi Dave
We took a day trip to Tangiers Easter 2007. Six of us bought tickets direct from the ferry terminal in Tarifa, from memory around 55 Euro's. this covered ferry, coach trip,guided tour and lunch ! Fantastic value and a fantastic day, a must do.
I don't know if this is the best way to see Tangier but we had no complaints, it's a different world.
We also found it quite easy to park in Tarifa 5 minutes from the terminal
Regards
Keith and Niki