Sometimes when the audio signal has a large crest factor (is that the right description? I mean when the signal has some really loud bits that look big on the audio event in the project window, compared to some really soft bits that look small), it’s better to even the volume out some before sending it to a compressor - it often will sound much better after compression if we do that.
Here are some ways to even out the volume in the project window:
- Using the Draw Tool (aka, Pencil Tool, accessed by hitting the number 8 at the top of your keyboard): The No.1 trick for LOUD mixes - Gain-Stage like a PRO in Cubase #cubase #mixing #gainstaging - YouTube
Pro: The audio track isn’t cut into lots of little bits like in option #2, below.
: Also, one can really fine tune the selection of the part of the audio you want to make softer.
Con: It can only make the audio waveform softer/smaller, as written above.
EDIT per @raino post below: There is a way to make the audio waveform louder/softer using this Pencil/Draw Tool technique, and it involves making it louder via the Info Line first: Select the audio event … go up top to the Info Line and type/scroll in a positive dB number (i.e., greater than zero) … see the audio waveform in the Audio Event get larger 
… now use the Pencil aka Draw Tool to bring the waveform down as above, and if you do that to a lesser degree than you have increased the volume, you have effectively made the audio louder/bigger than baseline as recorded. A trade off here is that using this method to increase the gain involves cutting up the original Audio Event into smaller Audio Events, which may be important to some. Simply decreasing the gain as above keeps the entire Audio Event intact.
- Split Range Method:
-Create a Range encompassing the part of the audio you want to make smaller (by hitting the number 2 at the top of the keyboard, left click, then hold/drag).
-Do the “Split Range” command. You can access this from EDIT (at the top left) > RANGE (drop down menu) > SPLIT . This cuts your audio segment into three parts, the middle part being the one you want to lower the volume/size of.
Note, SPLIT will be grayed out unless you’ve created the range first, as in the previous step.
Note: This “Split Range” process can be done with a handy key command instead of the more cumbersome use of the drop down menus as described above (I use a SHIFT X key command to do this, I can’t remember if that’s a pre-assigned key command, or I assigned it myself.)
-Go back to the Object Selection Tool (aka, Arrow Tool, by hitting the numbe 1 at thetop of your keyboard), click on the little white box at the top of the new (middle) segment of audio you created in the previous step (that’s the segment that encompasses the bit of audio you want to make softer; you might have to zoom in on that segment to see the little white box), then drag down till the audio size/volume is where you want it.
Pro: It works!
Con: Compared to the Pencil Tool method above it’s harder to get fine control of how much you want the audio volume/size to be reduced - the whole segment is reduced by one amount, determined by how much you drag down from the little white box at the top middle of the segment.
: The audio track winds up being cut into lots of little bits, which can make it easier to make a mistake later
: Like the Pencil Tool method, it can only make the audio softer/smaller waveform, can’t make it louder/bigger. (Note - as pointed out by @raino, the Pencil Tool technique can be used to make the audio louder/larger waveform when volume on the Info Line is first increased, see above).
- Using the Gain Function method:
-As in the “Split Range” method above - create a Range encompassing the part of the audio you want to make smaller (by hitting the number 2 at the top of the keyboard, left click, then hold/drag).
-Open the Gain dialogue. You can access this from AUDIO (at the top left) > PROCESS (drop down menu) > GAIN .
Note: This “GAIN” dialog can be accessed with a handy key command instead of the more cumbersome use of the drop down menus as described above (I use CTRL SHIFT G, I can’t remember if that’s a pre-assigned key command, or I assigned it myself).
-In the GAIN dialog window, type in how many dB you want to make the audio softer/smaller or louder/bigger. Watch the size of the audio in the range you selected get bigger or smaller, depending on whether you entered a positive or negative dB value in the GAIN dialog window, respectively.
PRO: This is the only method of the three that lets you make some parts of your audio louder/bigger! Yayy!
: Like the Pencil Tool method (#1, above), the audio track isn’t cut into lots of little bits (like it is in the Split Range method, option #2, above), maybe making it less likely to make a mistake later on.
CON: It may take a few times working in the GAIN dialog window before learning how to make things work in there, and until then it’s kind of fiddly and awkward. It gets lots better after a while, though, and once you get started you can move left to right across your audio track making volume adjustments really quickly.
DISCLAIMER: There is no Cubase guru at the keyboard at this moment in time (though I love Cubase and making music, being only an intermittent weekend warrior I’m actually much closer to being a newbie than a guru).
So, there may be: errors in what I wrote above, and I’m sure there are other ways to do clip gain adjustments, and I wouldn’t be surprised if they are lots better than the ones I’ve listed here.
So, smart guys if you happen to come by and read this later, please post corrections/suggestions, and I’ll edit as needed!
I hope this helps someone just starting out! 
