1) SMILE!!
2) Include/involve people
3)Take a leaf out of Elf. Sing!!
4) Let people know you're there for them
5) Hug!!
6) Encourage
7) Compliment
8) Do something entertaining
9) Be WEIRD in a way that gets others to join in
10) Give someone a simple, handmade gift like a drawing, poem etc.
11) Take silly pictures
12) Start a conversation
13) Teach someone to sign the alphabet
14) Take an interest in things others are interested in
15) Laugh; with, not at
16) Be positive, even about yourself
17) Write a positive message on a slip of paper and leave it for someone else to find
18) Tell someone they're beautiful/lovely/handsome/amazing etc., and mean it
19) Write a letter. Don't type an email; write a letter to someone, telling them what you've been up to, and send it. A handwritten letter beats ten emails anyday
20) Remember good times together; like in-jokes