Thanks to all for the advice. Please keep posting any other advice by the way, everything helps.
@Al Innella, what kind of melodies would I play? Would I play Arban's exercises or Orchestral Excerpts or what?
@applebrass, Those videos were great by the way, really helped me understand how things work.
One more thing, for Grade 7 exam in a few weeks time I have to play Sonata Breve by Takacs. It's quite a blow, and I have to finish with one loud and and clear high C. The problem is that about 50% of the time that note comes out as a Bb, and even when it does come out correctly 4/5 times it comes out soft, and there is no brilliance in the tone like with my other notes. I believe one of the reasons why this happens is because I am not used to pitching up that high (most of the time I only have to go up to an A/Bb, not a C) and this song requires me to play up to a C#. I do get those notes sometimes, it's just more of the time I don't, and it frustrates me to have such an anti-climax at the end of a brilliant piece.
What could I do to try and improve this? Would it be the same as what has been said above?
Also, in regards to pedal tones, I can usually go down to a low A, but I find it hard to get any lower than this. How much should I practice my pedal tones?