Talking is one of the best ways of getting to know more about someone, and talking to your girlfriend is the best way to forge tight bonds with her. It is very possible that years down the line, the two of you will remember many of the things you will say to each other in these younger days. These fond memories play an integral part in most long-running relationships.
One of the best ways of having a good, healthy and wholesome chat with your girlfriend is to start with small talk. The small talk will give you a general picture about her likes and dislikes, as well as what she would like to discuss and what she would rather leave alone. Once the small talk gives you a general idea, you can go ahead and discuss your common likes and dislikes. A wholesome chat can also end up in a decision to do something you can enjoy together. For example, a chat about the latest movie or play can actually end up in the two of you standing in queue to buy tickets for it.
As you begin to form opinions of your girlfriend during the course of conversation, she in turn does the same. Therefore, you should think carefully before speaking and taking up subjects that might be repugnant to her. Religion and politics, for example, are subjects which often do not gel well with breakfast, lunch or dinner. Unless and until you are open and ready for an active debate, those topics should not be touched with a barge pole. Talking about it, however, gives you an indication of your girlfriend's political and religions leanings.
A chat is one of the best ways to express your love to your girlfriend. But you should never utter the words "I love you" unless you mean it. This is because false love is very easily found out by women. In addition, most girlfriends enjoy hearing it, but do not make yours hear it all the time or she may begin to find the otherwise-well-meaning utterance tiresome.