Surveying from baseline / offset Start by roughly dissecting your garden as shown with the long pink line. Put a wooden peg into the ground at each end (in the case of a patio you will have to tie it to a chair or heavy object. It does not have to be parallel to anything but we are going to project off of this at right angles so take the easiest route possible.
Surveying from baseline / offset Now tie a small piece of string or electricians tape at regular known intervals i.e. 50cm or 100cm. Now simply measure across from your line, maintaining a right angle, until the tape touches an object or boundary. Reproduce all of these dimensions on your paper and fill it in like dot to dot and you will have a simple plan.
Recording data To record points of interest, measure along the tape (or, baseline), then take a measurement at right angles from the tape to the point you wish to record. Plot these measurements on to your graph paper. The accuracy of a right angle can easily be checked by basic triangulation (3-4-5 triangle).