I am the same as you wanting to earn Distinction for each exam I take. Puts more pressure on us, I know, but it keeps me motivated to try harder and not give up.
Currently my lessons are currently revolving around the Preparatory Grade but my teacher throws in a lot of Grade 1 stuff. She thinks the Preparatory Grade is too easy for me, and I am somewhere between Grade 1 and Grade 2. At this stage I will be taking the exam in the first half of the year.
Preparation at this stage is: scales, arpeggios, and a few easy pieces. My teacher wants me to get used to vibrato as well, as she says that it impresses the examiners at this level. Now it is really boiling down to my ability to keep practising as much as possible.