If I have a guitar tab like this
E---2--2---------------
B--2-------------------
G--2-2-----------------
D------3---------------
A----------------------
E----------------------
_______^___ how to play this line?
How can I play two different notes at the same time?
You could pick them simultaneously with two fingers of your strumming hand. In this case with your thumb (d-string) and middle or ring finger (high e-string). If you play with a pick you could as well pick the d-string while picking the high e-string with your middle or ring finger (you should hold your pick with your thumb and index finger).
As an alternative to Matt L.'s answer:
If you want to strum with a pick and not play fingerstyle, you can use your left hand to mute the strings in between the played strings. In this instance, use your left index and ring finger to finger the notes, while resting your middle finger softly on the B and G strings to mute them.
This will result in a more muddy sound though, so use this technique only when the music allows for it. Matt's answer is what most guitarists would advise you to do.
The way I do it while fingerpicking is use thumb for D and middle finger for E. I am assuming you are using a pick.
If you want to strum, you can mute the B and G line by playing a dead note, that way you will play those two strings only, but you will have an effect added, which you might not want.
If you are using alternate picking, the common way to do it is by using the thumb for D while simultaneously playing the E line. The common convention is to use the thumb, but that being said, use any technique you are comfortable with, it's not about HOW to do it, it's about DOING it.
Thumb and ring finger/middle finger OR flatpick and ring finger, but it would take more than that small sample to give a good answer on the approach. I know what it would not be, the muting method... not in this instance coming from playing those notes. Difficult and bad result.
