It depends on the reason why your friend is sad and whether it is a male or female. Women usually like to talk about why they feel sad. You can invite her to have coffee and cake or a drink in a nice hotel. Seeing a funny movie works for males and females. If it's a guy who is sad, I suggest that you invite him to watch his favourite sporting team or participate in a sporting activity that you both can enjoy. He might want a few beers in a pub as well.

there are several ways. 1º you may introduce him/her new persons ( as human being we're, we like so much to meet persons) 2º take him/her to club ( you'll see there isn't anything so good as to step up) 3º give a gift ( everybody likes to receive an amazing gift )