When do you add reverb?

Ok I will try to help ya here Optimus.  Welcome to the forum!

   My guess is that (like many people starting out) you tend to add too much reverb and that can make them sound like they are a half a mile down the canyon singing.  I did it too.     I would suggest setting up a bus and put the reverb on the bus set to 100% wet, then put a send from your track to that bus and mix to taste.  I can say that unless your going for a really dramatic verb effect in most cases you don't use much.  play the whole song turn the verb up til you notice it, then back it off a hair.   now if you play the song the verb won't jump out at you but if you muted the verb bus you would notice something missing.    
     As to the "air" you are looking for you will probably find that using an EQ.  try adding a high shelf to your vocal and bring it up until it sounds crisp and airy, again don't over do it because this can bring out some issues with your "Ssssss" sounds getting annoying (which you can fix with a Desser).  
I hope that helps.

" I would suggest setting up a bus and put the reverb on the bus set to 100% wet, then put a send from your track to that bus and mix to taste."
 
Thanks for the suggestion ChuckC, but this highlights another of my inadequacies. I have tried using busses but nothing seems to happen. Obviously I'm missing something crucial here. I don't seem to get my head around the idea. I usually dump the effects into the effect bin of the relevent track, then
bounce the lot down to one stereo track.
 
So some help here would also be appreciated I guess. 
 
Ohgrant, I'm afraid you're way ahead of me here. What is convolution reverb and cabinet impulses.

Ok, we are heading back to mixing 101... (it would help to know what version of sonar you are using)

  Alright well let's say you were mixing a song with 8 channels of drum tracks, 4 guitar tracks, a bass and 3 vocal tracks.   If you only have tracks and one master bus  and towards the end of the mix you find the drums are a little too low, you now have to raise equally 8 drum faders.  Are ya with me so far?

go into mixing console view, on the right side of the master fader right click and add a stereo bus, name it "drums" and set the output of the bus to master.  Now at the bottom of each drum track change the output to go to "drums" instead of master.  (you need to do this when the music is stopped not playing).   Now you can raise and lower the drums as a whole instrument or add effects to them as a whole!  You can do this again for guitars, vocals, etc.          
   Now, add a bus called verb and set it's output to master, add your instance of reverb to it's FX bin.   then you can go to your vocal tracks (or vocal bus) and (in mix console view) right click and add send, assign the send to go to the verb bus.  kinda works like an aux output.  I generally turn the "post" off so that I am sending the singal pre-fader rather than post fader.  If you don't do that and move the fader of that bus/track it will effect how much signal you are sending to the verb bus which can screw you up sometimes and levels go haywire.

   So in summary,  All buses do is make mixing a little easier and allows for the processing of multiple tracks together (like adding compression to all of the guitars as a whole rather than as individuals at the track level) or sending multiple instruments to the same reverb to put them in the same "sonic space". 

So right now lets say you have those same 16 tracks all going to the master bus.

We want to set up so that you have:
8 drum tracks-->drum bus --> master bus
4 guitars --> guitar bus--> master bus
1 bass--> bass bus--> master bus
3 vocals--> vocal bus---> master bus

Then sends from either the vocal tracks or the vox bus --> verb bus--> master bus

Seems complicated but it will make your life a lot easier I promise.

Thanks ChuckC, printed your instructions and will try out tomorrow. Yes I see the logic in it but it will have to wait till morning.
It's 1.45am down here in Aus and I need my beauty sleep.
 
Many thanks 
 
 

Busing is important, but that's not going to change the actual sound of the reverb itself.  You are likely describing the sound of a plate reverb. It adds length, but it doesn't necessarily put the vocalist in a particular "space".

Aside from the UAD EMT 140, my favorite plate reverb plugins are Valhalla Room and Audio Damage EOS.  Perfect Space has some plate impulses that you could try out.

I think the other thing to consider is reverb, not as a traditional long wash, but short reflections to give instruments space from each other.
 
For example, a lot of times on hobby mixes you will hear a guitar panned hard to one side. If you solo it, you would hear it only in one ear, very unbalanced because in real life you cannot hear something like that naturally unless you are deaf in one ear.
 By adding a very short ambient room reverb, pan it to the opposite side and voila! an instant sense of space.

Early and often, wetter is better.
 
And Altiverb, go big or go home!
 
http://www.audioease.com/Pages/Altiverb/
 
 

Thanks all. Lots to read and experiment with and think about.