Something like love at first sight
and how to regain her details and to try her once if dere is a chance To avoid losing her :- experts and great peoples give some solid genuine activities

That's a very silly but deep question...if you meet a girl and fall in love what you should do is to let her not to forget you by showing some uniqueness in your behavior or talking..because she sees a lot of guys and you're just one of them...so don't be just one of them..i stress it "don't be just one of them"..you should be very practical and positive minded and you should show deep interest and care in her..for this you must see and talk to her often..you can give gifts...you can give a call/message...
do everything you can do to make her fall in love with you..and the key point is Love&Care that no girl can refuse...