Purchase a copy of your lot plat from your County Recorder's office. This record is inexpensive to acquire. It usually shows exact measurements of your property, the boundaries, elevations and so forth.
Visit an art supply store and purchase a few large sheets of drawing paper similar in size to those used for blueprints.
Measure your home's plot size and shape. Start at one corner and work to the next until you have measured the entire property. Write the measurements down in your notepad.
Add measurements for the house, other outbuildings, walkways, patios, decks, swimming pool and driveways. If you know of existing septic tanks, or underground cables and pipes, make a note of where these are located -- you may or may not end up using these on a basic landscape design, but the information is good to have.
Draw the mapped measurements onto the paper(s), laying the home, building and other objects in their appropriate locations. Use the top of the map as "north." Add in simple sketches for trees, shrubs and vegetable or other garden areas.
Consult with a landscape designer if you prefer someone else draw up a map of your yard. They'll take the measurements and do professional sketches. Alternatively, you can use software made specifically for landscape design. Once you get past the learning curve, you'll be able to view different possibilities for your home's landscaping plans.