this may sound weird, but there are words you can get in your vocabulary that sound more intelligent than hum, um, like, etc... so if you think about it.. try to replace those words with things like:
for instance, particularly, especially, in regards.. i know they don't seem to match the conversation but lemme give you an example:
Me talking to my friends: Hey.. so I saw this really cool thing in lab, and it was like hanging off the side of the table... um, the red one in the back... and it was amazing, it kind of um, reminded me of that movie... uh.. frankenstein...etc.
Me talking to interviewer: While I was in lab, I saw this really interesting object that I had never seen before. IT particularly reminded me of a scene I remember from Frankenstein.
Okay.. that was weird.. but do you get the idea.. you can always use descriptive words to replace uhs and ums and likes and hmmmmmmms