I'm sure others can explain better but I'll give it a shot.
Multiplier and being "Stylish" are the 2 main things that give you more points.
You want to keep your MP meter going. If you get hit or fail to kill an enemy in a certain amount of seconds, your MP will reset. If you look in the upper right corner where your MP is (within the hexagon), you'll see a timer that goes counter clockwise. It's very faint and blends in with the background. That's the time you have in between killing enemies before it resets.
You want to always make sure there's an enemy nearby so you can continue your MP. That's why sometimes it's good to lure them to each other. If there are enemies that spawn on either side of you but you notice they are somewhat far, you can get close enough where one spawn follows you and then pick them off one by one, while moving to the other spawn. So shoot one, slowly make your way to the opposite side, then shoot another. Keep doing that to group enough enemies in order to earn some stylish points.
Stylish points are when you kill a group of enemies in 1 shot, but this doesn't count when you use your blaster. Only for the other 3 special weapons. IMO, the Energy Sword is the best for this. Get some enemies together and you can kill, for example, 8 enemies with one swoop. Keep doing this when they're around you and you'll rack up the points.
Energy Sword is best when they are surrounding you.
Laser is OK. You can hold down the button then turn left and right to take out enemies. which will keep the stylish counter going, but if you Laser someone then take your finger off the button then start again, the stylish counter will end. Hope that makes sense.
Missiles can get you out of tight spots. My second favorite.
Don't forget to pick up the small, yellow items enemies drop when you kill them. That recharges your meter for the special weapons. They'll be times where you emtpy out the meter and it'll go red, which means you can't use any special weapon for a few moments until it automatically recharges (but not fully). Do your best not to reach that point but if you do, no biggie. Just use the blaster to pick off enemies one by one (slowly..like, shoot one and wait a second or 2 then shoot another) until it recharges.
There's some balancing you have to do between the Blaster and the other weapons. You don't want to kill everything with your Blaster because you want to group up as many of them, but you don't want to go crazy using your other weapons and end up killing your meter.
I hope this helps.
