This simple jig makes laying out circles a breeze. Drill a 1/8-in. hole through every inch mark on a ruler or yard-stick. To draw a circle, place a pin through the number “1” into the center of your board. Add 1 in. to the radius of the circle you wish to draw, and insert a pencil into this number. Using the pin as a pivot, rotate the pencil to mark the circle. — Edwin Constantino. How to Cut Curves in Wood
Tape measure: I know this isn’t a power tool, but it is the one tool that you should always have with you. It is a pet peeve of mine – if you are planning on building something, or you are actually building it, have a tape measure with you. If you are in the shop, on the job site, or even at Home Depot make sure you have a tape measure with you or at least one very handy (Home Depot probably isn’t the best example, since they have them widely available, but you get the point). Without a tape measure, not much beyond rough work can get done.
Unless you’re a big fan of frequent shop remodeling, planning the layout of your workshop early in its development will save you a lot of time and trouble and also can keep you from spending years in an uncomfortable, poorly organized space. And if you already work in a shop that’s as organized as a trailer park after a tornado, careful planning and a little remodeling is likely to help you make a quantum leap.