Well I know exactly what you are talking about and I'm sure most people have experienced at least at some point in their lives what you are going through. My advice would be : First thing, just get OUT OF YOUR HEAD. Don't over think what your going to say or what the other person's response is going to be like. By doing that you are restricting yourself from starting what could probably be one of the most amazing conversations you've ever had. Second, start having opinions about everything around you. You don't have to be rigid. You can be flexible about it but what you should really do is accept yourself, respect your opinions and understand that not everyone is going to have similar opinions. At least by having an opinion on things you can easily strike a conversation with someone. Third, the way you express yourself matters. Instead of reacting to things, start responding to them. For example, if you disagree with someone then instead of arguing with them try to understand their point of view while making them understand your perspective. Fourth, take baby steps. Start by speaking for the trashcan. Talk about absolutely anything that you can think of and slowly build on it to see what you can talk about with the person. The funny thing is most of the time we don't connect with people because we have something in common but it is because we actually have SOMETHING to talk about. So stop looking for common interests and just let go of yourself. Put yourself out there and get rejected. It'll be fine as long as you take it up with the right attitude. Good luck! Take care <3