Ghana4Life has excellent advice. Follow it!
In addition, a simple rule: Don't give money and you can't get scammed.
If you really do want to part with money for no financial return, give it to a worthy cause like Kiva.org that provides micro-loans to small businesses in developing countries--people who are trying to make a legitimate living and not scamming online. At least you can see something positive come out of this.
I've sat in cafes in Accra (Sharpnet near Koala) that have private rooms and listened to young men in adjacent booths talk out loud with each other about the person they're corresponding with online. They comment about the photos, about how they're playing them, about how they're going to make money, about not being women themselves (when talking with foreign men who think the Ghanaian is female when they're male)...my partner and I considered doing a whole series about this on our blogs as it's endemic.
The number of times I see what look like twelve year old boys, not in school, chatting online in Yahoo with both old men and women makes me sad.
I would really forget this. Or, continue but don't give any money for months, as Ghana4Life suggests. Get to know everyone very well first. Know the family. Talk to them online .Call them at random times to ensure they are who they are.