I have had dogs all when I was growing up, but never had to train one. I adopted a dog, yesterday, and the dog is very sweet to me. He did fine in the dog park and walking along the trails in Philadelphia. I decided to take him with me to pickup something, in the beginning while waiting by the door he would go up and greet everyone who went in and out. After about 10 minutes, he started growling, barking and standing on his hind legs. This behavior is new to me, the dogs I previously had growing up were all very nice and never exhibited this behavior to humans. Now, I get he has only been in the city for a day, but this behavior worries me since I cannot avoid people on the sidewalk and don't know if he will sniff or lunge at them. This behavior seemed to be out of protection of me since he was standing pretty much under me while barking at times.

Any suggestions on what to do?

I have had dogs all when I was growing up, but never had to train one. I adopted a dog, yesterday, and the dog is very sweet to me. He did fine in the dog park and walking along the trails in Philadelphia. I decided to take him with me to pickup something, in the beginning while waiting by the door he would go up and greet everyone who went in and out. After about 10 minutes, he started growling, barking and standing on his hind legs. This behavior is new to me, the dogs I previously had growing up were all very nice and never exhibited this behavior to humans. 

Now, I get he has only been in the city for a day, but this behavior worries me since I cannot avoid people on the sidewalk and don't know if he will sniff or lunge at them. This behavior seemed to be out of protection of me since he was standing pretty much under me while barking at times.

Any suggestions on what to do?