It's a question of practice. It might be a good idea to reach out to one or two professional mediums and ask for advice - they must have gone through the same process as you. They might be kind enough to share some practical strategies that will help you. Another suggestion is to contact others who are also going through the same thing.
To hone and improve your gift, try keeping a detailed journal. You'll see I've given others here similar advice, so have a read through some of the other questions.