What gear have you got and what level can you play? Eg, can you alternate pick, palm mute and play power chords? If not, start there. Good death metal is the same as any other good guitar playing - Necrophagist, Death, Nocturnus etc all have the same techniques that Metallica, Satriani and Malmsteen use - they just play different music. Techniques are all the same, only difference is tone, the actual note structures and the degree of difficulty.