I generally don't have much of an attention span. It takes me a long time to read a book because my mind is always drifting. I get bored easily and find that I always need to jump around. I like things to be dynamic and always changing. I feel a mix should be this way, too. I feel that your brain subconsciously adapts to the levels of the guitars, per say, and gets used to it. The last thing I want to happen in one of my mixes is the listener's brain getting bored. Anyway, I had to write an into paragraph. Let's get to the real meat.

1. Guitar solos
   People often ask me how I get guitar solos to jump out in a dense punk or metal mix with very thick rhythm guitars. They also often ask me why their mix seams to fall off the face of the ear when the guitar solo is over. How do you keep the mix rocking the second the often very loud solo ends? Easy. You put a volume automation on the rhythm guitars. This can be a pain in the ass when you have 30 guitar tracks, but I'd still take the time to do it. Let's just assume that we have doubled guitars for our example... one on the left and one on the right. Immediately when the solo kicks in, I'll reduce the guitars by 1dB or so just to give the solo a little room. If you are listening for rhythm guitars, you'll hear it, but if you are listening to the song, you'll never know the rhythm guitars lost a bit of level. Then I go to the end of the solo. Depending on the song and how the solo is played, I'll find the perfect spot where the rhythm guitars should jump back in. Now back up just a little bit. I don't just keep my rhythm guitars at -1dB. I ramp them downward. THIS IS CRUCIAL. I tweak every song and solo differently, but there have been times when the rhythm guitars were down by as much as 4.5dB each when the last note of the solo was played. Then you really have to find the sweet spot to hit the guitars hard. If you can set your volume automation right, your guitars will seam to explode even though they are the same volume as they always were. This is just one way that you can trick the brain into getting excited (hopefully). Won't this make the rhythm guitars sound weak during the solo? Well, yes. It will take some energy off the rhythm guitars. However, guess what, you are pumping that energy into the guitar solo. Now if the guitar solo sucks, then you are out of luck. However, if Mr. Lead Guitar is playing something exciting, then this trick will make his solo shine even more. I use this on just about every guitar solo I record these days.

2. Lead Vocals
   You can't possibly tell me that every vocal track you've recorded from every vocalist has been at a perfect level. If you haven't recorded a person who needed a syllable to come here and a scream to go down there, you haven't recorded enough vocalists. In fact, I don't think I've recorded a vocalist who didn't need to be automated a little bit. Actually, I don't want to record a singer who doesn't need to be automated because that means they are singing like a robot and not singing from the heart.
   
   Mixing is all about getting the most emotion out recorded tracks. Sometimes a singer is going to whisper and sometimes they are going to yell in the same song. You'll want to bump up the whispers and you'll want to knock down the screams. Obviously, this makes sense, but can't you just use a compressor? I can't think of a time when I didn't compress the vocals. However, you would probably be totally compressing the vocal track to death to get whispers and screams heard.

3. Background Vocals
   I find that I automate the crap out of background vocals. I usually have to. To get the singers to blend well, it's usually necessary to automate every word, but not always. I have no problem with taking 10 minutes to make sure that background vocals are blending as best as they can with the lead vocal. If it took an hour, I'd still do it.

4. Everything
   Verses are generally softer and choruses are generally louder. Sometimes new tracks will come in at these times to make the chorus bigger. If it doesn't, you'll need to create some excitement. So get busy. It's amazing how differently a mix can sound when parts jump in and jump out at crucial times. Maybe a clean guitar is strummed for half the verse and then on the last half it's picked out. You may want to accent the picked out part if it adds to the song. It may need a ton of volume added. If needs it, then give it some volume! You are trying to improve the way the song comes across with volume automation. You are looking for little things that add and you are making them a little more obvious. You can take away junk that doesn't add. A further testament

5. Utilities
   Sometimes one snare hit will jump out way louder than the rest. I'd love to keep it that way a lot of the time, but due to the mega loud nature of modern recordings, it appears that it's more important for the song to be louder than it is for that one snare hit to jump out. So, I'll usually go in and knock that snare hit down to a level that is more consistent with the rest of the track. This has nothing to do with music. It's just something you may have to do every once in a while to ensure that your tracks are loud enough.

Conclusion

Your mixes should bounce all over the place. If you have done your job correctly, you'll have an exciting mix that the listener gets pumped up about. No one will know that you bumped levels here and cut levels there. Some may argue that you should leave a mix to be natural. Well, that's why I use volume automation. I want to make the band sound as exciting on the cd as they do live or in the room.