A best friend should always have these things:

HONESTY

KINDNESS
LAUGHTER
GENEROSITY
LOYALTY
EMPATHY

to make... THE MAGIC OF FRIENDSHIP (from MLP/MLPEG)

Also, a true, true friend should accept people for who they are and what they do.

Here is the video for the original song:

watch?v=5tCPxXW_9qI

If you want more about friendship, watch any MLP/MLPEG videos or the following:

Beauty and the Beast(full movie)

Cinderella(Full movie)

Harry Potter and the Philosopher's Stone(full movie)

Harry Potter and the Order of Phoenix(anything on Dumbledore's Army)

Hetty Feather(full movie)

The Railway Children(full movie)

the secret garden(full movie)