Most publishers' addresses are listed in the front of their books. An Internet search is also a quick and easy way to find addresses. The best advice I ever received was to write what I like to read. They also will tell you if they accept unsolicited manuscripts or if you must have an agent. Unless you have an agent, it can take from six weeks to six months.
Rejections come in letter form.
You'll get a phone call if they are buying. If you want your ms. There are books with lists of agents, and RWA also can help. This covers everything from finding agents to setting up your manuscript. If you decide you need an agent, your best bet is to attend conferences and meet several before approaching anyone.