what type of tweeking can i do to my bow to make it faster without sacrificing shootability? beyond the obvious, lighter arrows,increase poundage,draw length....i heard, twisting the string?adding 4 nocks with shrink tubing to the string near the bottom cam?please comment, i,m not very knowledgable on this..thanks

Other than the obvious that you stated, not much. Best bet if applicable to your set up is to get everything possible off your string, ie Kisser button, peep sight and rubber tubing, etc. Any weight you can remove from your string will be more energy that can be transferred to your arrow to get it moving faster.

jca-

Twisting the string will shorten the drawlength of the bow a tad, and add a little more bow poundage deflection to the limbs.

Adding the nocks to the string with heat shrink is a version of the "speed buttons", and from what I've tinkered with- it can be very "trial and error" to find the appropriate placement. You can actually lose a bit of speed if they are not in the optimum placement. You need a chrono and some tinker-time to get it right, or even to experiment to see if it's worth it at all. Out of a given bow, you mention the things that will affect speed. Arrow weight, bow poundage, and power stroke (draw length of the bow).

Like Range mentioned, ANYTHING on your string will slow your speed down. Cat whiskers, brass nocks, d-loops, etc....