Saying “Hi” — just kidding. Starting a conversation is hard; it really depends on the setting, the person’s style and demeanor. Usually, I observe the environment and try to find a common topic to comment on and create an opening. For example: music playing in the background, something showing on a TV, a shared activity like a party, or even being on the same means of transport heading to the same destination — weather talk, the classic small talk.

Come to think of it, this probably varies from culture to culture. I guess I find it easy because in my culture, that kind of openness is really common.