Step 2: Getting Started
Plan, plan and plan! Draw you plans out (as you have the measurements right?) on paper.
Then transfer your design to the garden. I personally use chopsticks and balls of wool as both are cheap.
Measure from your wall/fences etc and stake with a chopstick. Once you have 2 stakes connect the 2 stakes with the wool to make a visible line. Obviously a bright wool is great at this point (I use red or orange).
I drew my ideas in Sketchup.
As they say in the Army: "Proper Planning Prevents P&#% Poor Performance!"