Good luck. I think my favorite piece of equipment is my refractometer and my second favorite is my calibrated site glass, third is my digital thermometer. Right after that is software to record measurements and interpret what they mean on the fly (I like Beer Alchemy).
Knowing where you are is a big part of figuring out where you are going. With a preboil gravity and volume I can determine almost exactly what my OG and volume will be into the fermenter. If I need more sugar I sparge some more before starting the boil, if that means I get more volume than I expected to get the sugar I need, then I tack some time onto the boil.