Here's a super basic production question for you all. Thanks in advance for any advice you might provide.
 
I know you're supposed to keep the output levels below the "red zone" in the meter, but doing that always seems to make the overall mix too soft. Compared to professionally-mixed music, mine is always less loud. So I find myself stuck between exceeding the red zone and having adequate loudness, or staying below the red and having low output levels. What a conundrum. Does that mean everyone else is mixing in the red, or there's some fancy mixing technique I don't know about? (I've tried things like Boost11, but that makes a marginal difference.)
 
I'm making electronic dance music, btw.

In the case of EDM, Limiter plugins are your best friend, especially on the drums.
You mention Cakewalk's "Boost 11" . . . probably not the best limiter plugin, but may get the job done depending . . .
just don't use it on a whole mix ?
 
Izotope , Elephant, and Fabfilter really get it done properly, with many additional quality options.
 
Also, look into LUFS . . . the loudness standard for internet music . . . ie. if you exceed the LUFS too much, your online music uploads will just get squashed too much, and sound overly compressed on most sites.
 
I like to mix to -6db . . . then add subtle limiting to get the level up to these "new" broadcast (LUFS) standards.

Loudness is a psychoacoustic term. A lot of physical energy dBspl (the stuff that is measured by most meters) can be released into the world without necessarily resulting in the perception of loudness when interpreted by the  listener. 
Here is a simple read that may help you understand that the amount of red is not the most important thing in the mix. It should be evident from this kind of understanding that loudness is best managed at the mixing stage and that what can be done in mastering an already mixed channel is limited.
 
https://www.getthatprosound.com/hacking-your-listeners-ears-9-psychoacoustic-sound-design-tricks-to-improve-your-music/
 
 
 

 
I set this at   -.4 db 
There must be 1,000 of articles on this subject. 

Use The Glue from Cytomic.
The best I have ever heard.

https://cytomic.com/glue

Put it on your Master Bus.

As mentioned above, there are thousands of articles about loudness/mixing/mastering on the web, but anyway.
The simplified route to a loud song is:
Arrangement (that, for example, doesn't include too much frequency overlapping of instruments)/per track volume automation/Equalisation/Compression (per track and master) / limiter.
 
Use commercial songs of your liking as reference, and compare their frequency curves to those of your projects  with an analyzer like Voxengo SPAN (good and free).
 
One common mistake is to leave "unnecessary" lows in the mix. These are often almost inaudible, but do push the meters to red. Many dance/hiphop/whatever producers say they put an EQ cut at about 40 hertz on the master.
Also, for example power guitars or vocals don't need the low end hums and booms to sound right, so they can be cut higher. The low end/left hand of a piano/organ easily collides with bass guitar, so you must often give the room to either one of them. Etc. etc.

noynekker
In the case of EDM, Limiter plugins are your best friend, especially on the drums.
You mention Cakewalk's "Boost 11" . . . probably not the best limiter plugin, but may get the job done depending . . .
just don't use it on a whole mix ?

 
Do you apply the limiter plugin to every track independently? Can you apply it to a bus with multiple tracks sent to that bus? 

Cactus Music

 
I set this at   -.4 db 
There must be 1,000 of articles on this subject. 

Is this a screen capture of the actual setting (-.4db) you use?
 

Bass frequencies carry a lot of energy, and the build up of bass frequency energy over a number of tracks can make your mix peak - even if it doesn't sound loud.
 
One thing that can help is to roll off the bass frequencies of everything that isn't a bass sound.
 
Solo each track, then start rolling off at 30 to 35Hz, and work your way up until you can only just hear a difference - then back it off slightly so it has no audible effect.
 
If you've got a sub bass track as well as your main bass sound, you could also try this on your main bass sound and let the sub do all the work on the low frequencies.
 
[EDIT] - Sorry @Kalle Rantaaho - just realised you've basically said the same thing!
 

Neuroharmony
Do you apply the limiter plugin to every track independently? Can you apply it to a bus with multiple tracks sent to that bus?

You don't want to add your Limiter on your tracks, but place the limiter on your Mix Bus or your Master Bus.
I don't place any plugins on my Master Bus, I use a Mix Bus instead. The Limiter you want to use so that the overall level of the music doesn't go above 0db.   Now, if you are having tracks mastered, then you should set he limiter a lot lower to leave head room for the Person mastering your music,  However, if you are like most of use who just want our music mixed as good as we can get it and make it sound loud, set it for-2 or -1db.
 
See the Video on the this you Tube Channel 5 minutes to a better Mix.  Subscribe, as he has a ton of great tutorial.
 
Take advantage of the Waves L1 Limiter. you can revert back and forth between the new and old display. Waves L1 VIDEO