I have had a lot of drummers ask me about my blast technique on the snare, so I will attempt to explain here. The most noticeable trait of my blast technique is my elbow: it sticks out like a chicken wing at ninety degrees from my body, placing my hand near my ribs. I have my wrist pivoted and “hang” my hand from it, so that it looks like I’m about to punch the snare drum. It’s difficult to explain beyond this: by combining my wrist power and my fingers, I end up moving my left hand in a “doorknob” motion (a revelation Phil of Rellik and I came to over some Icehouse a month or so ago). Sometimes I lean more towards my wrist, or more towards my fingers, depending on the speed and length of the blast.
They don't make memory locks for everything, so you have to get creative. I have my drum rug marked off with duct tape, so that I know EXACTLY where to place everything. I also have my cymbal arm tilters marked straight across with a black Sharpie. When the two marks line up, you know you're set. This has saved me HOURS of setup time at shows, as well as in the studio (plus, your bandmates can't give the excuse "I don't know where it goes" anymore!). The lengths I have gone to to simplify setup is legendary, but, with a little extra effort, it can really help you.
(Ok, I kinda stole this one from Gene Hoglan) I find that most drummers in death/black/grind metal tend to use small diameter, light sticks most of the time (The smallest stick I will ever use is a 5A, and that's already pushing it for me). Last year, I had been warming up with a far beefier stick (I use a 2B for this purpose) on the first 3-4 songs of any set, and it had cut down on my overall fatigue, as well as improved my speed considerably. You can achieve the same effect by putting light ankle weights on for double bass. I have since moved on to the "middle of the road" sized 5B model.
Anytime you learn a new rudiment, be sure you know it inside and out. Push it to (and beyond) the limit. Play it as fast as you possibly can. You may never have to play it at that speed (and believe me, just because you can, doesn’t mean you should, anyway!), but, to go to any extreme as a musician means that any level of performance below that extreme is much simpler. (Ex: if you can play 64th notes at 240 BPM for 5 minutes straight, playing 64th notes at 120 BPM for 3 minutes with be nothing to you.)
Explore different muscle group combinations when playing usual double bass licks. You’ll find that you can pull out the same patterns for longer with less fatigue and/or cramping.
Want more speed out of your snare hand (or is it getting tired)? Use your free fingers to push up on the base of your stick, to lever it down towards the head. Use this in tandem with your wrist to develop a “seesaw". You’ll cut down on fatigue, and keep your snare strokes even and powerful, even on blast beats.
Think you know everything? You don’t. No matter how long you’ve played, or how much you have learned, there’s always something you haven’t seen, someone that can play faster, or a technique that you haven’t tried. Never stagnate. Be open to new ideas and other perspectives to the instrument.