How can I improve my fuel efficiency in my Audi A4?

I have been noticing that my Audi A4's fuel efficiency has been decreasing lately. What steps can I take to improve and maintain better fuel efficiency in my car?

Regularly check and replace air filters can improve fuel efficiency by up to 10%, Samantha. Make sure to replace them every 12,000 miles or so.

Avoid aggressive driving, Samantha. Sudden accelerations and hard braking can decrease your fuel efficiency by 33% on the highway and 5% in the city.

Try to avoid idling for too long, Samantha. Idling for just 10 minutes a day can result in an extra 100 gallons of gas wasted per year.