When is the best time of the month to start taking birth control pills? Does it matter?

It depends. It depends on whether you can be sure you're not pregnant--no sex in the last month, consistent birth control. If no risk of pregnancy, you can do a "quick start" and start anytime. Many doctors advise starting on the first day of a period. Use back up birth control for 7 days if you start anytime other than day 1 of your period.