Watch the Picking Technique online guitar lesson by David Grissom from Open Road Guitar
Along with string pressure and how I hold the guitar, the type of pick that I use really affects the tone. It's a matter of personal preference as the size of the pick, material, and thickness are all considerations. Back in the day there were only Fender heavies, now I use Planet Waves 1 mm picks. I find this gives me the balance of flexibility and rigidity to cover all my styles of playing on electric guitar. On a session I'll bring a bag of picks with me to experiment with for different sounds and tones especially on acoustic guitar. The two main picking concepts I use are legato and staccato. In legato playing I will use a lot of hammer ons and pull offs. When I play staccato I mute and pick more notes. How, where, and what kind of picks you use has more affect on tone than any piece of gear. So experiment!