It's not hard. Hold the door open for someone carrying a load of stuff. Smile at the people you pass. Say good morning. Say good night. Compliment someone, sincerely. Say please. Say thank you. Send someone a note, or a card. Tell someone you appreciate them.
It doesn't take much. I think we're all just out of practice. I think that every small gesture returns to you ten fold. Maybe you will make someone's day.