There are at least three basic types of Stick in the ground weaves, if you have anymore suggestions, let me know!
You can also use Caution or other tape, put grommets in it at 20" intervals - makes it a lot easier to place them.
Type 1 - Electric fence poles
These are poles used for electric fence, the best kind I find is the step-in type for ribbon fence.
They cost about
$2. Fairly easy to reposition.
Very hard to get in heavy or compacted soil.
Type 2 - Rebar covered with PVC
You can buy rebar (used for reinforcing concrete), hammer it into the ground, and put a piece of PVC over it.
Type 3. You can take a 3/4" end cap and put a nail or a sharpened bolt through it.
A good instruction on how to do this is on this page.