First of all, this is directed as an exercise for men but theres no reason ladies cant do it as well. Anyways:

Before you start approaching girls on any given day, it helps best to have had at least one interaction with a stranger that day. It reminds your brain that strangers and interactions with them arent as scary as your brain tells you.

So guys, try this: When youre walking down the street, spot a dude that you dont know, go up to him and act like you know him. All you need to do is say "Yo whats up man" and put out your first for a fistbump. Once you get the fistbump, keep walking. Thats it. If they react harshly (odds are they wont), just say "my bad, I thought you were someone else".

This helps get me into the rhythm of talking to strangers and reminding myself that if you are the confident, you can make any situation feel normal. Hope this helps.