What's best practice to make batteries last longer?

Leave it plugged in 100% of the time and only let the battery cycle once a month or by accident or rare use.

I have a cycle count of 14, it's "Normal", a 97% charge and the machine is over 26 months old.

I actually beleive now the more one cycles the battery and the lower the remaining power it has when it's recharged, the more it wears it out.

What will kill Mac laptop before the battery is the small vents at the back of the fans that get clogged with dust bunnies, that will cause the machine to overheat and draw more power on battery etc. wearing them out faster.

Also using the built in keyboard/trackpad, the Superdrive as a mega cd burner and high use of the Ethernet, audio and USB ports tripping over their cables.

Use wireless and replaceable external devices as much as possible.

You might find these two articles will answer your question:

http://www.apple.com/batteries/notebooks.html

http://support.apple.com/kb/ht1446

Ciao.

This question has been asked before and I always turn my MBP off but others put theirs to sleep. The consensus is that it really makes no difference so you pick what you prefer.

Ciao.