Definitely treat this like a normal job interview. Prepare as you would for any interview, though if it’s informational, make sure you’ve got some good questions prepared. A lot of time, people will judge you based on the quality of your questions; through the questions you ask, people can learn a lot about your intelligence, curiosity, creativity, and ultimately what matters to you.
FYI, my last two full-time jobs were converted from “informational” meetings. Always be overprepared rather than underprepared.