How to ask for more money starting

I just had a phone interview and am invited to an in person interview next week. Originally, the recruiter said starting pay was $18. The phone interview I had was with who would be my manager and I asked him if the starting pay had wiggle room. He said that is something I have to discuss in the in person interview.

I am hoping to get $20 but am not sure how to go about this. Everything about the job that was described to me sounds like things I've done before so I know I will have no problem doing this job. Anyone have experience negotiating a higher starting pay?