battery

Hi, I Just bought my new MacBook air 2days ago; and I have a question regarding its proper way of charging. I have been searching a lot lately about how to charge it properly, but I can't seem to find a precise answer concerning this. My question is: is it better to charge my MacBook from 20-100% and put it to sleep? or should I charge it 10-80% to make my battery life longer? And also, what is more advisable- to use it while plugged or put it to sleep while plugged? Thank you so much!