1- Always be mentally ready to pick up
There are attractive women all around us — at the supermarket or waiting on you at a clothing store, in line at the bank, on the street... So... why don't you try to pick up a girl where you are at the moment? Maybe you would be successful.
But remember: Girls don't expect to be hit on as they go about their daily lives, and, therefore, they are that much more flattered when it happens.
Most often, just strike up a conversation while waiting in a store, based on what's going on around us. You could comment on the wait ("I hope there's a meal at the end of this line"), what she's chosen to buy ("Huh, I looked at that but passed it up. Have I made a mistake?"), or anything, really. It could be on the street, too. The point is, you have a few moments to notice a hot woman, then look around, think of a clever line and deliver it in your most confident manner.
But approaching strangers is, in itself, a little nerve-wracking, let alone hot women. A good way to improve your skills is by starting casual small talk with random people — both men and women whom you're not necessarily attracted to. Then you won't feel the pressure of impressing them. If you're already pretty comfortable chatting, then next time you see a woman you like on the street you can approach her without being nervous.