This is a common issue with new puppies that can cause quite a bit of frustration and pain. Here is the scenario: the puppy often starts out being playful, but then gets worked up and starts nipping feet, pants, long skirts or anything within reach of his razor-sharp puppy teeth.
One client dealt with this every morning while she got ready for work.
One of the more frequent issues with shy dogs is to be afraid of getting petted by strangers. When dogs are getting petted the person is close to them, they are looking at them, they are looming over them and then they touch them. These are all potential triggers for anxiety or aggression. If your dog is shy, you should help her get comfortable with people to avoid escalation of anxiety which could potentially lead to aggression.
There are a lot of misconceptions about playing tug with your dog. In my experience, (and lots of other trainers I respect) as long as you teach your dog some ground rules, tug is a great way to condition your dog to have a soft mouth as well as providing your dog exercise.