When you just start you engine you should Keep your car engine tuned for few minutes and its tires inflated to their proper pressure so you will save gas. Like I call services because I thought my tire was broken but it wasn't still there were air inside!
Shop around for gas check online for pricing compare those price with different gas station and get lowest octane this may save you hundreds of dollars a year.
When driving, avoid fast start-ups and stops you can't avoid this in traffic unfortunately

Over time, you will save hundreds of dollars on lower gas and maintenance costs and try to find better tricks and deals for gas!