Let me give a counterposition to balance things a bit.
First: most nowadays music does not touch hearts. Many agree with this. But this music is produced by many of the engineers hanging around here. So be careful when listening to the masses here. Always listen to the different positions and find your own.
Second: start using a splitter (I guess an active one that splits into two signals with the same impedance, but ok, I did it with just a y-split-cable and it worked too...). There are some variants in splitters. You connect it to the output of your preamp. Then you record one signal without processing and the other goes through your processing chain (lets start with a compressor).
Some people seem to say that it's good to route the compressed signal to the singers headphone too (there are reasons for this, but I can't exactly remember). They say the singer does a better performance when he fights the compressor (maybe this gives him more push / emotion). Monitoring for the singer is sure very important.
Now you have 2 signals and you can make your own mind up. It's at least very good for learning. Use your ears. Learn to hear the nuances.
Don't record too hot into a DAW (-12 to -22). It's a different story if you are using tape, but I guess you don't.
Now there is the position: if you compress a little in each stage (recording, mixing, 2bus, mastering), you get the best results, at least better than compressing once heavily. This also depends on the musical style. In dense rock you might have to compress more to keep the vocals standing out. But these arguments are just one side of the coin.
Other people will argue: compression will kill your emotions (transients, dynamics, etc.), it will kill your frequency range (making it slightly duller), etc. You can never add, what you have lost. And you can still compress later which gives you more security and freedom.
I just tell you one thing: make up your own position on this. Don't believe what they tell you - at least not blindly.
And read: Bruce Swedien - Make mine music. He explains a lot about vocal recording. And he talks a lot about microphone technique and room etc. And I believe he never even mentions a compressor at tracking. This guy knows about recording. But maybe he is working with tape, and there is some compression happening there too... so you see, this is a complex topic.
Check Micheal Jackson recoring vocals after you read the book: http://www.youtube.com/watch?v=2uloW...eature=related
You see how he is working the room?
It also depends on your singer as mentioned above. But especially with dull sounding men, try to keep their natural frequency range...
Also try to experiment with parallel compression, if you like.