Basically, there are 2 keys here:
1. comfort--this comes from repeated interactions and gaining a sense of mutual familiarity,
2. commonality--working or studying or playing or volunteering towards a common goal. Working at the same company, attending the same school, or joining smaller organizations at work or school allows you to develop positive feelings as a result of doing something positive together
This is all best accomplished with people at the same or similar life stages. Teens and college students tend to take lower wage jobs in retail, younger adults in college and grad school, etc.