Two things that have helped me reach semi-perfection with chocolate chip cookies are: a cookie scoop and parchment paper.
There aren't too many kitchen gadgets that I would promote. But the cookie scoop is one I'm ready to affirm. It only took 9 years of marital bliss to break down and buy one, albeit at a thrift store for $2! :) The cookie scoop makes the dough in uniform balls therefore taking the guess work out of the process. Plus - it was super fast to make these 12 dough balls.
As for tweaking recipes, I follow the exact directions on the back of the Nestle Tollhouse semi-sweet chips. I even preheat the oven. After nine minutes on the dot, I take out the pan. The cookies will appear a bit under cooked. They will firm up a bit more once out of the oven. I promise.
See those golden edges? This is where the parchment paper is paramount. It takes the cookie from being yummy to being yummy AND pretty. Slide the paper off your pan and onto the cooling rack and scoop up more dough.
The best part of using parchment paper? The clean-up!