How to maintain optimal fuel efficiency in my Vauxhall Combo Life?

I've noticed a decrease in my Vauxhall Combo Life's fuel efficiency and I'm wondering what steps I can take to maintain an optimal level. Any tips?

Regularly checking and changing your air filter can greatly improve fuel efficiency.

Properly inflating your tires to the recommended pressure can also help improve fuel efficiency.

Avoid aggressive driving and excessive idling to save on gas.