My dog barks at everything and he wont stop?

I got a second dog and when I got him he was quiet for the first month (most likely settling in). However, after 2 and a half months he won't stop barking. A few examples: When I go to the garage to get a drink out of the fridge, he barks. He barks when everyone isn't in the same room and won't stop which makes things difficult if someone in the house is upstairs. If I plan on taking him and my other dog for a walk, he will bark at me and try to shove my other dog out of the way as I try to put her leash on. He will continue to bark until I have him out the door. He also barks if I give any attention to my other dog and not him or if it even looks like I am going to pet my other dog. One of the major problems however is that he barks at lawn mowers that are more than a block away (making Sundays a real problem). He also barks at pretty much anything else. I am thinking about getting him a bark collar but I wanted to know if there were any kinder ways of doing it.