Exactly measure lumber for cabinetry
Get yourself a good quality folding measuring stick like that pictured below. These have a slide out bar that allows for exact inside measurement transfers to be made.



One useful technique for marking in a precise manner is to use a sharp blade to make a cut mark instead of using a pencil. The cut is much finer than a pencil line.

Another useful technique if making multiple pieces the same length is to cut one length from some scrap wood and use it as a template length. Again use the blade to make a short cut mark for the length. Use of scrap piece helps to ensure you always use the same piece for measuring as opposed to picking up the 2nd or 3rd piece for the next measurement.