There is nothing you can say to make her interested.

Interest i.e. initial attraction happens almost immediately. This means that if you fail an approach it’s not necessarily (and likely not usually) your fault. You should be fit, well groomed, etc. but that's another post all together. You can make attraction happen, but if it's not there to begin with you'll be fighting an uphill battle. With as many women that exist in the world there just isn't any reason for that. You're not trying to make her interested. You're just trying to make conversation.

Some of the best advice is to ask any question and LISTEN to what she says. It doesn't have to be complicated or clever. To be honest I don't like putting a lot of effort into what I say. If the initial attraction is there then it's on her to make herself interesting to me. You are making the approach, so she should have to put in some effort in return. Use what she says and "pull strings" from what she says to make conversation. Girls LOVE talking about themselves, and you barely have to do any real work. If it dies, tell her it was nice meeting her and move on.

React to what she says. If it’s funny, laugh. If you’re outraged by something be outraged. If you don’t feel anything don’t do anything. Do not force them, just react honestly. If you’re really listening you will not have to feign interest.

Tease her. If she says she hates tomatoes and you think they’re the shit tell her she must have messed up taste buds. The last girl I was with told me she liked Hozier and I said that after listening to some of their songs it was easy to see why they’re kind of a one hit wonder. Of course she got really defensive and even pretty angry. The point is not that she was mad about what I said. The point was that I made her FEEL something. Both strong positive and negative emotion are useful in creating a meaningful conversation.

Don't forget to ask for her number so that you can meet and talk again later. Even better: take her back to your place to talk more.

Here’s the most important bit.

If you haven’t talked to a girl in the last few days, or the last few weeks, or months, or years, or ever you need to ban yourself from this subreddit until you talk to some people. Join a club, volunteer, talk to someone at the grocery store. If you’re not doing that then this PUA stuff is hurting you way more than helping. Keep it simple, find a sticking point and come back for help. Not you nor me nor likely anyone else here is important enough to worry about the outcome of approaching a girl, so do it. With as many as are a part of this community there should be a lot more FRs.