Pup never barked and now is really bad

hi there pup never barked and is barking at all guys that walk past and try's to jump up on them.when out for walks she really barks a lot in house when the door goes,belllas nearly 8 months,please help thanks in advance

 

Here is lots of good information on barking - http://www.thelabradorsite.com/labrador-barking/

 

Hi. Have you tried doing 'LAT'? (Look at that). As soon as you spot someone you say 'look at that' and reward her for no barking. I would keep her as far away from the trigger as you can to start with and slowly move forward but constantly reward for not barking or pulling. It's not a quick fix, but does need to be consistent.