Watch the Week 2: Tone & Dynamics online guitar lesson by Roberto Dalla Vecchia from Flat Out Flatpicking
Guitar tone depends on a number of things, let's focus on your picking hand and your pick.
Let's start off by looking at what kind of pick to use and how to hold the pick. Picks come in a wide variety of shapes sizes and thicknesses. It's a good idea to go down to your local music store and buy a variety of picks so that you can see what works best for you.
The angle of the pick on the string is something that you need to be aware of. Some players angle the pick up or down and some keep the pick parallel with the string. This is more of a personal preference but I have found that most players angle the pick downward. I would encourage you to look up some videos of your favorite players and see what their right hand technique is like.