Hitching is never entirely safe in any country, and we don't recommend it. Travelers who decide to hitch should understand that they are taking a potentially serious risk.
If you must otostop (hitch), you should probably offer to pay something towards the petrol, although most drivers pick up foreign hitchers for their curiosity value. Private cars are not as plentiful as in Europe, so you could be in for a long wait on some routes.
As the country is large and vehicles relatively scarce, short hitches are quite normal. If you need to get from the highway to an archaeological site, you hitch a ride with whatever comes along, be it a tractor, lorry or privates car.
Instead of sticking out your thumb for a lift you should face the traffic, hold your arm out towards the road and wave it up and down as if bouncing a basketball.