This link from MakeUseOf.com has some great tips. Probably the coolest are the unit conversions which often saved my life in engineering school:

Google can do painful conversion for you, for example from degrees Fahrenheit to degrees Celsius. It can also answer really mundane questions such as what is the time in Sydney. Just type your question in plain English and Numbers, and Google will most likely give you a reasonable answer.

This lets you skip going through a million conversion tables, or lets you easily calculate how much gas will cost per person for that road trip you’ve been planning.