Doing these things that I'm going to mention below has really helped me develop more confidence. People who just want a bit more confidence can also benefit I hope.
First: get rid of your negative thoughts, don't allow yourself to wonder about how people will react and so on.
Second: don't think before you act! Confident people usually just do it they don't think. (Very similar to first one but it's not really negative thoughts it's just thinking in general) and don't think about it after either!
Third: coax yourself out of your comfort zone as often as you can. Don't like sitting in crowded places? Do it! Don't like running by yourself? Do it!
Fourth: relax!! Just relax! Take a breather and calm down. Whenever you feel nervous or anxious. We are all just people at the end of the day. All just people.
Fifth: take little steps! And don't ever beat yourself up about something you didn't do for example you wanted to talk to the stranger but you didn't! So what! Another day!
Sixth: realise that people think less about you than you think about yourself! Honestly!!
Last one: appreciate and believe in yourself. Stand up for your beliefs and don't doubt yourself! You are confident! You are beautiful!
Life is so much better lived when you're not scared all the time. When you're just living and relaxing. (Most people aren't scared I suppose it was just me hahha)