I use “let’s see” sometimes.

I am sorry to say that the best practice, by far, is to avoid ANY kind of filler words. Listen to a good speaker, and notice that a short pause is not a problem. It can even help "punctuate" the speech. If you "freeze" and get stuck, just stop, take a few breaths, and continue. It is awkward while it is happening, but the audience will forget it immediately. There are two problems with fillers. a) They just do not help the listener. b) Speakers always get stuck on personal favorite fillers.

I use ‘so’ a lot! Then, because, well, like are quite common and probably used the most.

@Pip - Thanks! I must warn you there's a legion of people who detest "so" as a filler or introductory word. They're intractable, and I find it best to avoid getting them riled up.

@Dan Smith - Thanks! Actually, I agree about not using fillers. When interviewees stall with, "That's a good question," I want to answer, "I know it is, and that's why I asked it." Ok, I won't say that, but I want to. A student asked for suggestions and I wanted to see what the italkhivemindind came up with. When I studied French, I adopted "c'est a dire" when I got stuck. Silence would have been better....