If you are using existing toilets you will have little choice about their location. If you have to camp close to toilets make sure they are downwind of the rest of your campsite (your campsite should not be next to the toilets in any case). If you have had to construct your own, make sure they are in fact 'off-site' and downwind of the prevailing wind.

They should be clearly marked and screened from view. Ideally some washing facility should be placed by the toilets themselves. Latrines should be dug downhill of the camp and away from the water supply as well. You must be careful not to dig them too far away otherwise people will be tempted to 'go' somewhere closer to hand!