Thanks guys! I'll try some of those.
@Bazza - often I have an idea in my head but midway through articulating it, the idea just vanishes, and I just suddenly lose track of what I'm saying and what the whole point of the conversation is about. I think it's more to do with the fact that I'm focusing too much on how to articulate the particular idea, instead of trying to retain the idea in my mind and conceptually develop it. This said, the 'planning' idea sounds good!
@ matty - sometimes, I feel that pausing seems very odd and awkward for both myself and the person I'm speaking to. I don't know, I think, intuitively, I just feel that saying "um" or something along those lines is more natural, although of course it won't play to my advantage in the long run. But I shall try and get rid of it, slowly and painfully...xD