I generally water my cacti and succulents from the bottom, placing the plant and its pot in water to just over the rim, and leaving it there until all the bubbling stops. About every third or fourth watering, I drench the soil from the top, to remove excess salts that may be building up from my local water supply.
You need to make sure the root ball gets thoroughly wet when you water, then allow all excess water to drain off. Watering from the top all the time often fails to saturate the center of the root ball.
If your plants are in standard potting mix, rather than in a soil mix specifically designed for cacti/succulents, you might want to water from the top as a rule, but water from the bottom every third or fourth watering. Essentially, reverse the way I treat my cacti and succulents.
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams