Take a series of measurements across the facade of the house, noting the position of doors, windows, and bays. Also note the distance from the side of the house to the boundary. Mark all of these measurements clearly on your rough sketch.
Measure from one corner of the house to a point on the boundary, or a feature, such as a tree. Repeat from another point on the house to the same point on the boundary or feature. Note these on your sketch. To plot a curved or uneven boundary using triangulation, take measurements at about three-feet (one-meter) intervals. Draw the triangles and note the measurements you make on your rough sketch.
Peg a tape measure at 90 degrees to the house at a point you measured in Step 1, and lay it along the length of the garden. Lay a second tape at 90 degrees to the first to measure the position of boundaries and features. When taking offsets, use a giant tri-square to ensure that your tape measure is at exactly 90 degrees to the house, and that the second tape is at right angles to the first. If these angles are slightly out, your plan will not be accurate. Mark each of your measurements onto your rough sketch.