There are good reasons why discussions when you meet someone for the first time should be light.
Avoid sensitive topics and serious subjects. It's best to be silent and ask as many open ended questions as you can to get the other person talking.
The more your date talks the more impressed they will be that you're so interested in what they have to say. Also if you do all the talking, you'll learn very little about the other person. How will you know if you want to go out with them again?
Avoid discussions that sound like a job interview. Make it friendly, and fun. If you like each other, you can discuss more serious topics on future dates.
Don't get into personal information unless the other person brings it up first. Even then, tread cautiously. Look to turn the conversation around to something else. If they want to divulge secrets about themselves that's ok. Listen and pay attention. But if they want you to do the same, try to change the subject. There's no sense discussing important issues with someone you might never see again. On the other hand if you go out with them again, you can slowly start talking about matters affecting your new relationship.
Stay away from relationship discussions such as why you broke up with your ex or the nasty divorce you're going through or any troubles you might be having. Emotional baggage is a turn off and even if you're a perfect match in every way, your date may pass on an opportunity to see you again. So don't mention anything. Eventually once you've been out on a few dates and have established a romantic connection, they will become aware of the issues you're dealing with. Once again. there's no point bringing up sad topics on a first date. Avoid talking about your problems.
Avoid discussions that revolve around your life. Some people are very good at asking questions and you may find yourself wrapped up talking about exciting things that you're interested in. That's ok, but don't spend the whole date talking. Understand that the other person is being social and wants to know who you are. However if you want to impress them and see if there's any compatibility, it's best to have a balanced conversation where both of you are taking turns talking and listening. The best way to make a connection with someone is to be a good listener.