Xx

when reading TAB you see X's. I know that means that those notes are not played. I have been trying to practice doing that, but I cant find anything on this site that has pratice methods. Maybe I am missing them. Are they on here?

The best way I have found to accomplish this is to finger the chord so that you mute the "x" strings with the egde of the finger from the adjacent string. Try lookin up "fret hand muting". If the "X" is either high or low E just wrap your thumb to the top to mute it or rest your palm on the bottom on.

X's can mean a couple different things depending on how they are written. It's not always just "don't play this note".

Can you give us an example of what you are seeing?

An example would be, while looking at TAB you see notes then XX then more notes. While listening to that song you can hear the XX part. But it does not ring its more of a ching. Where they hit the strings but they did not sound.

It means that the strings are muted not with the picking hand but with the "playing hand". There's a couple of videos that explains that, I think in the guitar fundementals series.
Basically what you do is rest your fingers (of the playing hand) on the string and play it. It will cause a ching sound. Like Eric said, sometimes you have a full chord with x's in it. The trick is to have the nearest finger on the adjacent string touch it just a little so it dosnt sound or sounds "chingy".

Pretty much what SebastBerg said. In this case, you aren't NOT playing the strings. You want to play them, but just muted.