You don't need "lines" and "rules" to strike up a conversation with someone -- just a great way to help them open up and start talking. Ask them for a recommendation, like for a place in town to eat, favourite holiday spot, movie to see, or anything that asks for their opinion and helps them open up and start talking -- and gives you something to engage with them about.
Image from pamelav
Essentially, the trick is to give the person something to respond to with their own opinions (since everyone generally has an opinion on these kinds of topics). As a result, they open up to you, you make yourself seem more interesting, and you might even get some really useful information from the conversation.
Whatever their response, you've broken the ice, and the conversation can flow naturally from there. For more suggestions on great conversation starters, check out the full post linked below.