Learn to differentiate weed seedlings from desirable plants when they are small so they can be quickly eliminated from the garden. This Weeds Web site from University of Arizona Cooperative Extension has photos of common Southwestern weeds at different stages of growth.
Clever Gardening Technique
Time Your Weeding Sessions
Weed the day after rainfall or a scheduled irrigation. Weeds are much easier to pull when soil is moist and you're more likely to get the entire root system.