An easy way to increase the value and enjoyment of a conversation is to say a lot less and listen a lot more. This applies obviously in cases where the subject is something you're not an expert on, but can also be extremely valuable in those exact circumstances. Obviously there are limits to this advice, but they are probably much further away than you'd dare believe.
Also, people tend to assume that you share more of their opinions so you can make friends quicker too. You can't put your foot in a closed mouth.