how do you play tabs like this:
E --------------------------------|
B --------------------------------|
G --19-19-19-19-19-19-19-|
D ---x--x--x--x--x--x--x---x---|
A --17-17-17-17-17-17-17-|
D -------------------------------|??
You mute the D string with your index finger. (or any finger I guess) Rest down on it so when you strike it, the note doesn't ring out. You don't need to put a lot of pressure on the string.
Also try picking, depends on what the piece is though. Hold plectrum as normal pick the neares string with it and catch second or third finger on other note. You can pick 4 notes like this just takes a bit of practice.
Place your index finger on the 17th fret and your ring finger on the 19th fret, your index finger should be automatically touching the string in between thus preventing it from ringing. Then you just strum normally.