Quick energy orb regeneration technique (for Arcade/Zetsu modes):
-Hold A+C with your option on an enemy, and when you see energy orbs come out from the enemy let off A and then rehit the button. Do this in a slow rhythm (about once every second) and you will get more orbs in a shorter period of time. Do it too fast, and you'll suck in the orbs. This is the trick all the top replays use, if you watch closely you'll see their shot change from A to C and back to A over and over until a large amount of orbs are present.
Boss bomb item scoring technique (for Arcade/Zetsu modes):
-Like in DFK BL, it's best to let the bomb item float around the screen until the boss starts shooting bullets. Don't collect it in Fighter mode. Instead, you should change into Ninja mode, reflect some bullets, then collect the bomb item. You'll get a gold ring with a high hit count, which you can cash in for at least a few million points.
How to use lasers for score (again, just for Arcade/Zetsu modes):
-Every time you ram into a laser in Fighter mode you get a nice chunk of energy. It's useful to do this on purpose for score if your meter is empty, especially if you're coming up on an extend soon - the extend will give you a full new life block and regenerate the block depleted from the laser hit(s).
-On bosses, defeating them in Ninja mode turns any lasers on the screen into large point items, while bullets turn into smaller ones. So try and save the final blow for the moment when lots of lasers are on the screen (don't try and ram these lasers, it will turn their stream into bullets, which don't give as many point items).
- I assume this means you'd always want to be running on your last life if you want really high scores
Nope. None of the top scorers does that. Some suicide at the very start of the game for a little extra meter, but that's about it. If you know what you're doing you can score just fine with the default meter, it just requires expert energy regeneration techniques. Plus, you get 8million per spare life at the end of the game.