My favorite people are the ones with whom I can talk for hours or spend hours in silence, and neither is awkward. And I'd guess most of you would agree. And, by extension, most main characters would agree as well.
Unfortunately, however, I, you, and our characters, cannot always be surrounded with Favorite People. Which means there will be Awkward.
I say "um." I don't realize I say "um" until I catch myself doing it, and then it's like being aware of your own tongue in your mouth--awkward (oh hey), uncontrollable, and all-consuming. I notice every variation. Uh. Um. Er. Well. Ah.... Huh. I was watching my TV interview the other day (because I forgot what I said and was like, oh hey, I don't have to remember because it's recorded!) and ended up yanking on my braids every time I heard myself say "um." It drove me crazy. Crazier. But then again, if I'd articulated everything perfectly I wouldn't have sounded like me. I would've sounded...I don't know...rehearsed. And I'm not a good enough actor to make rehearsed sound natural. (Weird how that circles around.)
ANYWAY. Point being: Don't shy away from um in dialogue. I wouldn't suggest using it as often as a normal person does, because, um, normal people use it a lot. Take note next time you're listening to your friends. (Warning: this will probably cause some excessive teeth-gnashing...)
Also, don't forget about "like." As in, like, this. Because that is something people say. It doesn't have to be a parody, like, every other, like, word, like, that would be so, like, silly and, like, annoying.
But it is used. Sparingly, yes. But 'tis a fact of life. Or, at least, dialogue.
Um, over and, like, out.