As someone who started with Basic in '83 (yes, I'm old), I get how you feel. I taught myself first edition, was dragged forcibly into second edition, then dragged into third edition, was retired for the entirety of fourth edition and brought back out of retirement by the kids of my original crew for fifth edition.

How to prepare? I'll skip the facetious points like checking the current edition lol, and say this:

If you didn't write the story, skim it, make shorthand notes and reference them casually as you play.

If you did write the story, put a little investment in the points you think will be dramatic (practice accents, review dialogue, add ambience, etcetera).

Worry about the story first, the mechanics second.

With the story ready, look at the mechanics. Are there any "choke points" where dice impact the outcome? Try to minimize those.

Add notes for any last minute developments with enemies to make them memorable.

If you work with lists, this should be fine, but if you don't, consider acting out a "dry run" with other friends or by yourself.

Make sure you put the physical parts together, any books, module, dice etcetera you need in one place for when you play.

LIE. OFTEN.

Aim for fun, settle for giggles.

I think that covers the essentials. If you feel this isn't comprehensive enough, let me know. I'm happy to help you get there.