Most of the time you don’t need every little utterance included in your transcript, such as um, hm, uh-huh, OK (especially when it’s the interviewer), like, etc. unless it’s essential to the meaning of what’s being said. Those words are distracting to the reader – you want to read through the transcription smoothly. So if they’re just superfluous things that aren’t important, then best to leave them out.
Same with “false starts”. When people speak they often start a few words of a sentence, and then stop and start over repeating those same words or altering their words. Those also are distracting to the reader in a transcript, so it’s usually best not to transcribe those as well.
A transcript where every utterance and false start is included is known as a verbatim transcript. They’re often desired for legal transcription or things such as student or patient evaluations. But the vast majority of the time, they just throw off or slow down the reader.
In a related vein, when people speak, even in formal settings, they often use words like wanna, cuz, gonna, etc. In those cases it’s best that in the transcript, they’re written out as want to, because, going to, etc. – unless the transcript should be verbatim. Again, writing out want to instead of wanna, because instead of cuz, etc., results in smoother reading.
Similarly, depending on what the transcript will be used for, obvious grammar errors in the spoken speech usually should be corrected in the transcript, such as changing “she don’t know” to “she doesn’t know.” An exception is “ain’t” – it should be written out if the speaker says it.