I am currently training my puppy not to jump on people for attention. What I am doing is asking her to sit when she greets people and this way she gets attention. When she jumps up she gets no attention (fold arms, look away and turn away). When she stays sitting we go down to her level and give her lots of attention.
I am also teaching her to jump up on command and get down on command. This also seems to be working (she's not yet 4 months so slowly slowly,!) as a few of our friends don't mind her jumping up. I figure jumping is natural for dogs and if she only jumps up when asked then at least she can have some fun! I'm all for letting dogs be dogs, but I'm also aware that jumping up on children and frail people can be dangerous.
Some other people have also suggested try the 'ignore & turn away' method in conjunction with throwing treats on the floor. This way they learn 4 paws on the ground good, jumping up, not so good!
There are lots of different methods people use, if you search on the internet you can find some useful information, but use your judgement as I have read a few articles that I just don't agree with at all. If you read something and feel you are comfortable and able to do then I'd say it sounds like a good training method for you.