My best advice is to go to the local Spiritualist Church, make some good contacts, and after a while quietly ask if there is a closed development circle locally. It'll take time so have patience. As others have said, you may make a better healer so be open and sincere with yourself because Spirit often engineer paths for you if you are serious about what you want to do and if the potential is there for mediumship. I think it's an incredible responsibility because there are those "upstairs" who want to communicate that life goes on and pass a message on to loved ones who may be still grieving, and also those who bring a more profound message of survival and teaching of the ways of the Spirit. Accuracy is all inevidential Mediumship and this often takes time to perfect. But boy oh boy there's nothing better than seeing a quality medium letting fly, and the faces of the ones getting the messages. Wonderful and priceless in every way.
Being a good healer is of great importance too. To bring the ease of suffering to another is working for Spirit in a lovely way. It takes less time to perfect (mainly) It can be used just about anywhere, and if you are good then the rewards are again wonderful and priceless. Also dont forget that many a good healer has progressed to Mediumship.

G