you may find it easier to start by giving people eye contact and a smile or nod at first, then build up over a few times to saying hi, then maybe good morning, then gradually to I like your.... then when you are feeling more confident you will be ready to broach a simple conversation. it takes millions of grains of sand to make a beach, in the same way it takes lots of little steps to build confidence, don't be put off if you do not get a response, people may just be suprised that you are acknowledgeing them, they may feel shy or aprehensive too, but slowly slowly works.