Bending is typically reserved for electric guitars because acoustic strings are just too thick. In electric guitar playing, where string bending is an integral technique, the strings are thinner. Most use strings sets that start a .009 or .010 millimeter gauge (“nines” and “tens,” to use the vernacular). A light-gauge set of acoustic strings starts with the diameter for the 1st string at .012 millimeters, which is generally considered unbendable by all but the most dedicated masochists.
Here's how you play the bend on the 3rd string with the third finger, which is probably the most common type of bend.-
Place your third finger at the seventh fret but support the third finger by placing the second finger at the sixth fret and the first finger at the fifth fret, all at the same time.
The first and second fingers don’t produce any sound, but they add strength to your bend. Supporting your bends with any other available fingers is always a good idea.
-
Pick the 3rd string with your right hand.
-
After picking, use all three fingers together to push the string toward the 6th string, raising the pitch a whole step (to the pitch you normally get at the ninth fret.
Pushing your hand into the neck as you execute the bend gives you added leverage. Also, using light-gauge strings on your guitar also makes bending easier.
You can check to see that you’re bending in tune by fretting the target note normally and comparing that to the bent note. For example, if the bend indicates a whole step (1) on the seventh fret of the 3rd string, first play the ninth fret normally and then try bending the seventh-fret note to match the ninth-fret pitch you just heard.