The only things I know is proper breathing and developing a rythem with with your body while moving. The biggest thing is just experience sparring. I know that when I started I could only go 2 rounds sparring and I was totally gassed. Now I can spar 10 rounds. I'm basically in the same shape, it's just now I relax and don't burn needless energy.

I do wish to get more tips on how to relax more.