One way I found is to focus on someone's interest or hobbies and ask them meaningful questions. People will often open up to complete strangers when it comes to interest.

Be observant, for example, if someone is wearing a jersey of a sports team, ask them about the team, or the school it represents.

Look for suttle things, people love for the most part to be given the stage, when they feel comfotable with something they are familiar with, in the end its about finding comon ground.