Lexical Fillers... Sort of, Kind of...
So-called 'lexical fillers' are contextually meaningless words that folk use to fill in gaps in their speech when they are thinking what to say next, voids that would otherwise be silent.
Those of us who have to speak professionally (e.g. politicians, lawyers, broadcasters etc) are trained to try & avoid lexical fillers because, while they are contextually meaningless, (some of) the words/utterances in isolation do have meaning, therefore they can upset or, worse, distort the overall significance of what is being said - particularly if the listener is not fluent in the language of discourse.
If you listen to non-trained individuals speak on radio or TV, you can hear them use lexical fillers all the time, & of course, in everyday colloquial speech, most of us use them often.
For example, common lexical fillers in English are 'kind of' or 'sort of' or even simply 'ummm' or 'ehhh', e.g. 'I went to the doctor, and I was, eh, kind of, eh, nervous, and the doctor asked me to, um, lie down on, sort of, a table...'.
I wonder whether Spanish has common lexical fillers, and what they are...
7 Answers
In addition to the above, You often hear "¿tú sabes?" like the English "y'know". Oh, yes, también se oye "¿verdad? una y otra vez (repetidamete) ¿verdad? ¿verdad?
A veces esto me vuelve loca. (¿Verdad?) 
I thought of another common one, a ver.
¿Muletillas? Bueno, pues, este, a ver, mmm... O sea, ¿no? Si me entiendes, ¿verdad? Es decir, yo creo que, digo, hay muchas, en fin, no sé si me explico. 
I have a flash card set with filler words here and one on Memrise. The set from here was made by listening to conversations from former members here on Skype and I just wrote down the words I heard in the conversations. One member even did an exaggerated example of someone using fill in words so we could get an idea of how to "buy time" in a conversation where we need to think of the right word and don't want too long of a pause. This is the list I came up with. Filler words
This has a lot of other words too. Transition words Memrise
When we were in Catalonia last summer, we heard the word "vale" a lot. I was being used like "good" or "ok." An example. I ordered a beer, he ended that exchange with "vale." I paid him, he said "vale." He gave me change, I said "Gracias," he said "Vale."
Bueno, pues, (and depende, maybe?) are some of the words and there are non-word utterances, but I forget what exactly what they sound like.
Mae, en Costa Rica mae, usen "¿verdad?" mae, y "sabes" mae, y mae, a veces usen "ver" mae, pero usen mae demasiado más que todas. Mae es como "dude" en inglés mae.
Pura vida mae.
No lie, some use it to this extreme.
