Weed-b-Gon Chickweed, Clover, and Oxalis Killer.

Or you could get rid of the SoCal environmental catastrophe called a lawn.

i just pull them out. One of the most prevalent weeds here. It's a Euphorbia.

Good point from Sara. If you only have a few, onesie plants, then pull them out. If you have left them to spread through the entire lawn, then spot spraying them out is a more effective use of time.

Nil13 also has a point. I'm going to modify the point from his/her intent. If you don't get early morning fog until 11AM most days, then you should be growing a southern type grass like bermuda, St Augustine, or zoysia. If you live inside the morning fog zone, then you can still grow the southern grasses, but you can also grow the Marathon dwarfed fescues. So if you are east/inland of Inglewood or Costa Mesa, or Escondido, you really should not be trying to grow Marathon. Basically east of I-5 or the 405 is southern grass territory.

That? Easy enough to use hula hoe aka scuffle hoe.

Try vinegar..THEY say,because I haven't tried it, it will kill weeds. I still use Roundup..I can't bend over and pull weeds out of the many cracks here near the Hayward fault!

Can't use a hula hoe in a lawn...

If vinegar needs to be horticultural vinegar at 20-30% and the plants must be within 10 days of germination. And it won't kill the roots.