How do I keep dogs/cats from pooing on my lawn?

For those times when pet owners aren't around to pick up their beloved's excrement, then I suggest using motion sensing lawn sprinklers.

The animal comes near and they get 'pissed' on instead.

There are also other products like high frequency ultrasound deterrents that only animals can here and it is supposed to keep them away as well. You can get those on motion sensors too.

You could try Mothballs crush them up and scatter on your lawn,the smell of the camphor puts off dogs and cats...so the old gardeners tell me when the come to buy it from the shop that i work in.

Gatling gun

lol

Shoot the damn things with a BB gun. If that doesn't work you just increase the caliber until it does.

I've got very inconsiderate neighbors who let their cats overrun our condo complex. They don't bother picking up after themselves, much less their cats. The cats have decided to crap and vomit on our side of the parking space (which we unfortunately share side-by-side open spaces) not to mention our yard which their cats jump the fence to get to (our yards are so small there's no need for grass or sprinklers). Now our car cover is usually covered in cat vomit. What can I do to prevent the cats from choosing their "designated crap n' vomit spots?

Kick the owners behind.

Unless you are prepared to secure your property like Fort Knox, you cannot prevent cats from pooing on your lawn. The easiest way to prevent dogs from doing so is to fence your property. It doesn't require chemicals, you won't have to keep sprinkling things, etc.

a high powered squirt gun ....a few good zaps with that and kitty cat will find another litter box !

The most obvious answer to this question would be to train your pets at an early age. If you are referring to your front lawn and people walking by, don't really worry. Polite pet owners don't generally let their pets poop on your lawn!

Put a sign on your lawn that says "If your pet craps on my lawn, I will sleep with your wife"