What is the best way to show a girl you lost that you want her back?

The best way is to ignore her, let her come to you. If you keep yourself busy with other things she may come around.That increases your chances 50%, as it stands now chasing her will get you a 1% chance of getting her back.It's a 50/50 if you ignore her go about your business and if she calls or you see her be friendly but always say your on the way somewhere don't have time. Stop if you gave her many chances to dig you. Go try your charm on a more appreciative lady. Otherwise, date the girl. Get to know her and make her feel special if she'll let you. Tell her what you like about her and show her by your actions.