Human beings are social creatures by nature. We love to talk, about our interests, our thoughts, ourselves. We thrive on an exchange of thoughts and ideas, wanting to perpetuate these ideas and share them with as many people as possible. It's easy to get someone to start talking about themselves or things they believe in.
But conversation, like a relationship, is a two way exchange. One-sided conversations aren't very fun, and it's important to pay attention to those little cues in a conversation that indicate that you've lost your audience.
Keep Your Conversation Topical
I see this one time and time again. I'll be having a conversation with a guy - and we'll be talking about something really interesting - chemistry, or books, or games - and he'll suddenly turn the conversation to sex or my breasts or something completely off topic. At that point it feels like he's not interested in me, but interested instead in my body or just getting some. I cannot tell you how BORING that is. Even if I was interested in the man in the first place, derailing my conversation from the interesting to the wanton totally cuts that interest.
There are ways to gauge when the right moment is to drop those sort of subtle, sensual hints. And sometimes, it's okay to be brazen and open - but if you're going to do that, do it from the begining - and those sort of hookups rarely last beyond one nigh. This advice is intended for more for long term relationships - or just getting your foot in the door. When you do want to lead a conversation in that direction, it's important to let things move in a natural direction. Don't force a conversation into sensual, as forcing it tends to ruin the intended effect. Start small. If your partner seems interested, take it further. If not, let it drop.
Are They Really Interested?
Now, there are several cues to tell if the person you're talking to is really into you. Maintaining eye contact is important - if they're genuinely interested, they'll keep looking at you. People who aren't really interested tend to have eyes that wander, or focus on a single thing and glaze over. They also won't have any real response - instead, they'll nod and make noncommittal responses (Yeah, uh huh, of course). People who are interested lean in; people who are disinterested lean back, and people who aren't interested cross their arms over their chest in a defensive pose. If they're interested, they won't use breaks in the conversation to change the subject or keep checking their watches or cellphones.
Be prepared to discuss a variety of topics, and also be prepared to let the other person control the flow of a conversation. Try to get an idea of what the other person's likes or interests are, and direct the conversation on that course. For example; I'm one of those girls who likes games - which is easy for most guys to talk about. I'm not a hardcore gamer, but I can usually manage to hold my own in conversations like that. But gaming isn't all I do and it isn't something I want to talk about all the time. I also stay up on current affairs and I love to cook, which are two things I can really talk about for extended periods of time, but I wouldn't subject the average guy I met to a discussion on baking techniques unless I knew he was really into it as well. Most people have some level of common ground somewhere.
Important topics to stay away from up front - Religion and Politics! These are two very hotbutton issues with people, and should definitely be discussed, but only when both people are very comfortable with each other and can stand to be a little offended. It's easy to talk about both of them because people tend to be very passionate about them, but you never really know who you're going to offend by what you say with them so it's best to play safe until you have a better idea.
Of course, religion and politics can be dealbreakers, so you want to make sure that you discuss things before they get too far. But while you're getting to know someone, it's best to stick to safer topics.
Don't talk at people. That's a quick turn off for most people, and what makes people tune out the fastest, where someone drones on and on and never lets someone get the word in edgewise. Try to keep your answers brief, but informative, and don't dither. Remember, brevity is the soul of wit, and I'd much rather hear a quick, quippy comment than some long droning statement that takes twenty words to say what can be said in ten. Most people are too polite to point out when you're talking at them, so be alert for this common pitfall that can turn people off.
Give the other person a chance to talk too - even if you're not that interested in what they're talking about, be polite enough to hear them out, and you may be surprised at what you learn. Don't try to change the subject on someone, and try to let a conversation flow naturally from one point to another. If you're reminded of another anecdote, let them finish before going off on your own tangent - you'll win more points for listening than for dominating the conversation.