Personally I would encourage any pilot in training to get themselves a copy of MS Flight Sim and get a bit of practice with the online ATC through VATSIM.
I did this for a year or so before doing my PPL and it was a huge help. My instructor introduced me to R/T after about 7 or 8 hours and was amazed at how fluent I sounded, he was very impressed with VATSIM and now actively encourages his students to use it to gain experience in the comfort of their own home under no pressure.