"From time to time, you may notice that your laptop’s battery doesn’t stay charged as long as it should. This is sometimes due to the user constantly keeping the battery on mains power, or allowing it to only drop to 50% before recharging. Modern batteries are usually quite good at dealing with this, but every so often it’s a good idea to recalibrate your battery to get the best out of it.
You might want to check you’re laptop’s documentation, or check with the manufacturer to see how often you should do this. Sometimes they will say it’s not necessary, and sometimes they will say once a month, or once or twice a year. The response often depends on whom you speak to at the company and there isn’t a defined best practice. However, you can’t do any harm by performing a manual recalibration, so why not give it a go and see if it makes a difference?
Recalibration involves charging your battery to 100%, and then discharging it completely to 0%. Once that’s done you charge it back to 100% to complete the calibration."
Basically, fully charge it, use it until fully discharged, then fully charge it again. Apple has a quide if you want to read it in more detail, but fully charge>fully discharge>fully charge pretty much sums it up.