Sometimes the most obvious answer is the correct one, so I would check to be sure the faucet is firmly turned in the off position each time. Then I would see if the actual faucet joint needed tightening. After that, I would have to call on a professional, as I do not know much about plumbing.
Probably worn rubber washers/seals in the valve assembly. Replace parts in your faucet at a hardware store, but if there are a lot of issues, replace the whole faucet.
take the knob off and then go buy the inside washer and change them and toughen everything up and this should work i just did it to the down stair bathroom
Remove handle, unscrew base, pop up the stem, put in a new of rubber piece that sits on top of small spring. Press down hard,replace the base and handle.