In casual situations, I frequently use the words um, like, uh, and ah, despite being taught that these words are bad. (Hey, I'm a linguist. You'd have a hard time convincing me that "bad" is not an arbitrary label for words.)
Now what I've discovered is that I use each of these words in a fairly regular way. I think this is kind of awesome.
Want some details?
I use like directly before a word or phrase that I'm emphasizing, and usually there's a slight pause after like to add to the tension/stress/emphasis. For example: "I have to work, like, nine days in a row, all extended hours, and they're all night shifts!"
I use uh when someone has said something, well, that tends to be a bit obvious during a moment of slight stupidity. It's a moment for me to pause and not immediately call someone out on their mistake. It's a moment for them to correct themselves and for me to find a way to gently respond, whether I choose to address the mistake or not. Usually this is followed by "I think", as if I have an alternate opinion on the mistake or as if I'm unsure or might be mistaken myself. Interesting, no? Sometimes I use this to pause, as if I'm thinking, even though I know I'm right. (If I'm not right and I really am thinking, I use a drawn out hmmm or ummm.)
While ah is a common indicator of understanding or agreement in my speech, particularly when drawn out as ahhhhhh, I also tend to use it to introduce suggestions. As in, "Ah, let's make a trip to the store before we make plans for tonight." Or, "Ah, we should give that kitty a fine brushing."
So. Pretty cool that these little words carry more meaning than the sloppy speech they're usually labelled as, no?