What I am about to say will probably sound cynical. So be it. I do offer the disclaimer that I am not stating this as absolute fact nor am I stating it as applicable to 100% of conversations, merely 98%. Give or take. You know these conversations--the ones you do to be polite. Ready? Here goes.
The art of conversation lies not in how much you can say but in what you do say. In fact, the less you speak, the better.
The art of conversation lies in turning all your conversation toward the other person. Few people really want to get bogged down in the banalities of what you've been up to or what you think on an issue, regardless of whether they ask for said information. Do not assume that "How are you?" is an inquiry of your general state of wellness; it is merely the set-up for "Fine. And how are you?" which is an infinitely more suitable conversation topic than your domestic stresses or flare-up of rheumatism.
Listen with rapt attention to how poor Fluffy had to be put down, how your acquaintance's boss is an ass, and how his or her classes are going. Ask about his or her fondest Fluffy memory, the details of said boss's ineptitude, and whether acquaintance's profs are difficult. Follow up with appropriate croons of sympathy, appropriate righteous indignation at the gall of some people, and appropriate reassurances that you're certain this will be the semester to regain that 3.5 (or 2.5 or 2.0) GPA.
Does the above sound taxing? No worries; you needn't respond with full questions to each and every question or piece of trivia. Nod, smile, or even make noncommittal responses that suggest rapt interest. As a rule of thumb, consider the 37-1 rule. For every 37 words your acquaintance utters, supply one of assent or encouragement. They needn't be spaced at exact intervals; use your discretion to determine when response is required, and if you're damn good, when such prompts assist in the dramatic arc of the unfolding life saga.
Use the above advice, and I guarantee that your social acquaintances will find you a wonderful conversationalist. Just be careful lest they seek you out. Greatness has a cost, and the cost of conversational greatness coupled with cautious politeness is the danger of many lost hours. People can talk for hours about themselves*.
Now playing: Thrice - The Lion and the Wolf
* - Says the blogger. At least I admit to it.