I was at a fantastic weekend seminar with this US trianer, Dee Ganley. She has an excellent website full of training and behaviour tips. I liked this one on small dogs, which has some good advice for making your dog a more polite dog (not jumping up or assuming they have the 'right' to a lap etc) but also some good precautions around big dogs.
http://www.deesdogs.com/documents/smalldogbigattitude.pdf
http://www.deesdogs.com/documents/smalldogbigattitude.pdf