I'm learning "Last Christmas" arrangement for the acoustic guitar, and have encountered lots of notes marked as "x" in tablature.
--------------------------------0----------------
-3--------3-----1---------3--3------1------------
--------------------0-----------X-------0---0----
------------X------------------------------------
-3---3--------------------3----------------------
-------------------------------------------------
Seems reasonable, that those notes must be muted. But how? Especially when they are played together with another, not muted note.