After you shower or wash your feet, make sure you dry them thoroughly, as damp conditions make fungal infections such as athlete's foot more likely to develop. Again, focus and ensure that the skin between your toes is dry. Talcum powder or cornstarch can be used to absorb any excess moisture.
Change your socks whenever they become damp from sweat or if they get wet, because damp socks cause moisture to continuously surround your feet and provides the perfect environment for fungus to grow. If your shoes get wet, remove them, dry your feet, and stuff your shoes with newspaper to absorb the moisture. After this step, leave them to dry out before wearing them again. It may also be wise to get into the habit of wearing different shoes everyday. Even having just two pairs of shoes that you can wear on alternate days is a good practice because it allows your shoes to properly air out and can benefit the health of your feet.