How to get rid of weeds without using too much poison?

The most effective way is to pull them out by hand when the soil is damp, especially after rain or watering - it's much easier and gets all the roots. If you've got a large area, a weed burner (those gas ones) works well on paths and between stones without leaving any chemical residue. To prevent them from coming back, put down a good layer of mulch or even cardboard underneath - it really cuts down on new ones sprouting. If you still need something stronger, there are natural herbicides based on acetic acid (like concentrated vinegar) that are way less harsh than synthetic ones.