Draw the room on a piece of paper; leave enough room to add dimensions and notes. Make it large enough so that it is easy to add notes.
Measure the lengths of each wall using a tape measure, and write down the dimensions on the outside of the walls on your drawing. This will provide the cabinet supplier the overall dimensions that the cabinets need to fit within.
Measure from the left side of each wall to the center of any outlets or plumbing supply lines that may be present in the wall. Make a symbol for the outlets or plumbing and record the distance from the wall on your drawing. Do this for each wall that will have base cabinets. Note on your paper anything else that may interfere with the placement of the cabinets.
Measure and note any windows on the walls on your drawings. Most of the time you want your cabinets centered on windows that are in the room. The cabinet supplier will want this information when designing the cabinet layout. Note the location of any appliances and give their location from the left wall also.