How often have you gotten to the end of a two hour project and the audio just needs to be slightly louder? Most editors might want to start weeping openly at this point, but fear not, there is a quick and easy way to adjust all (or some of) your clips in one shot. Simply select all your audio, and press CMD+OPT+L. As you can see, the "Gain Adjust" window has opened, and you see that it's ready to have you input a number and press OK. Notice below the slider is a drop down menu with "Relative" selected.

If you selected your entire (or some of your) sequence, and were to input "3" as the value to adjust your gain by, and have "Relative" selected as your method of adjustment, pressing OK will add +3db to each clip relative to what is already applied. What this means is that if you had a clip in your sequence that was already at +8 db, the clip would now be at +11 db. This is an extremely handy feature to use to quickly adjust the levels of a group of audio clips. On the flip side, by adjusting the drop down menu to "Absolute", entering +3db will put the audio level of that clip at +3db, regardless of what the clip originally was.