Slight tangent:
I have the tendency to write battle scenes as bloodily as possible. This has nothing to do with my supposed attention to detail and everything to do with my
fetish. But it
does have the interesting side effect of making the fights more realistic.
Though, the scenes in White Rose where Higan and Makai's armies are fighting were not written with my fetish in mind! Rather, it's because there are few things on this planet I hate more than war, and in the same
vein as The Red Badge of Courage, I
really hate the mentality that war is glorious, so I go out of my way to make it horrific. One of the things I regret most is that because this is Touhou, fairies' wounds don't last, and ultimately the carnage turns out to be bloodless (damn that Hell of Blazing Fires) which is why there's a scene with Alice working in an almost Civil War-era field hospital to make up for it. My conscience just wouldn't let me get away with making war look less horrific than it is.
More on-topic: You want a way to learn to write good fight scenes? Then
watch a lot of them. Give your brain more material to draw on, and sit down with some movies that have the kind of combat you're thinking of. Space battles? Watch some Star Wars. Hand-to-hand combat? Watch some old-school kung fu movies. Danmaku is a bit harder, but
videos like this one can help with visualizing that. And when all else fails, play the fighting games-- describing those moves alone would make for some really good fights.