General tips off the top of my head?
-Practice Ki Pulse fluxing (the flux skill is in the skill tree and is shared between all weapons) when you get down to the bottom half of your stamina bar during a series of combos.
Yes, flux gives you back a chunk of stamina when you switch stance on ki pulse, but some people don't know that if you switch stance multiple times in a row on ki pulse, you get back multiple chunks of stamina. So after a multi-combo onslaught, and you're running low on stamina even with ki pulsing, do a ki pulse flux where you chain multiple stance changes and get back the whole bar.
-Learn an optimal punish when you drain a human enemy's stamina. Some people just go for a grapple. Don't do this. You can get so much more damage.
For example, when I break a human enemy's stamina (human bosses included) with dual kats, I Sign of the Cross, which knocks them down, then I position myself to where I'm directly behind them, do a final blow, then time a square combo as they get up. If you time it right, you will get a full free combo behind the enemy without them getting a chance to guard as they get up. Also sometimes the game lets me get in two Sign of the Cross attacks and still get a final blow in afterward. Not sure what the requirements are.
My friend who mains single kats hits a stamina broken enemy to knock them down, then does a fully charged Iai as they fall, then finishes with a final blow from behind into a square combo like I described above.
This does an extreme amount of damage compared to just going for a grapple.