I like these questions but I've never really thought about it much actually. I guess I'm the only guy here so far, I'll continue to work on promoting the community. Actually I've found that the forum on okcupid is really good for what I'm trying to do with this community.
Anyway, I think conversation is very important for a long term relationship. I want a girlfriend to be my friend. Friendship comes first, without that I don't see how you can have a long term relationship.
I think conversation is a really good indication of friendship. It shows that someone respects my intelligence and is interested in what I think about things. So conversation is probably a good way to have a guy stay with you for a long time. Communication is also essential to a long term relationship, so a good or probably necessary conversation topic would be the relationship itself and what each of you wants in a relationship.
So, if other guys are like me, we want essentially something that is a friendship, but a special kind of friendship. Talk to a date the same way you would talk to any other friend. If it's your first time meeting, talk to them say same way you talk to anyone else who you meet for the first time. You probably will want to talk about some of the basic details of the potential relationship especially if you are looking for something long term. But on a first date I think getting to know each other as friends is probably plenty. I think men and women both get nervous or shy, etc. and I don't think anyone is interested in making it awkward, so I think just talking as friends will feel natural and is probably fine.
I think on a first date conversation is probably easy actually, since you don't know each other you can just ask about each other.
After 3 months, or 3 years, etc. still talk to him as a friend. A friend that you've known for longer, and probably better and in some ways that you don't know other friends. Every friendship is going to be unique anyway. After a while the conversation topics that you have will probably be unique to the two of you.
I would like to mention that while I think it is somewhat unusual, I don't think it is necessary for a relationship to be based on shared interests. It is o.k. and even to some degree preferable to be different.
Last but not least, never force conversation to happen. Personally I'd be concerned if there was almost no conversation. But occasional times when you don't have conversation is fine.
Some people say a first date where you do something like watch a movie that doesn't involve conversation is bad because it doesn't involve conversation. Others say it is good because it's a way to have a first date where you get to spend some time with the person and meet them without the potentially awkward situation of not knowing what to talk about at say, a restaurant. Personally I don't know which side I lean towards, you might want to judge that according to yourself, how comfortable you are at making conversation. Of course you probably can't judge according to your date since it's the first date.