I'd say that depends on your current fitness level. If you're a beginner to strength training, I'd say 3 times a week to help build muscle. If you're more advanced, 1-2 times per week should cut it.
As far as when, the best time is whenever best works for you. But I'd make sure you do it at a time where you can put the most energy into your workout, because that's when you're really going to see results.
"I have a personal relationship with food. I love it, but it's on the fence about me." ~Kathy Griffin
"If there was a famine, we'd be the last to survive." ~My mother
| current weight: 137.8