I've recently been photographing some good friends and stuff like that. My sister and I will go out in the yard and I'll photograph her. Usually I stay away from that fakey posed stuff (which is hard to do sometimes) and try to get them fooling around (not acting like their drunk or doing stupid faces though, lol) by maybe cracking some jokes, getting them to run around, climb fences. I've taken some great photos(I think so) when they aren't even expecting me to take a picture, candids can really turn out great sometimes. I would ask your sister or any other family members, since you say your friends are too shy/etc. Once you can prove to them that you are a good photographer(by showing them pictures that you've taken of family/things/etc) then they might take you serious and want their pictures taken.
Also, let whoever you are photographing mix it up a bit by letting them come up with some ideas (but don't let them take over too much
).