You can’t do much preparation since you don’t know what they’re going to ask. You can assume there will be some “basic” programming questions, but that’s really as far as you can take it in advance.

My advice here is for during the interview: keep talking. You should always be talking. That’s how the interviewer assesses you. They want to know how you are deconstructing a problem and how you want to solve it. Sitting there silent for 5 minutes and then banging out some code isn’t giving them anything.

“Ok, I need to modify this array and I should try to do that in place. I need to look up the syntax for that because i rarely need to do this…”

“I don’t remember what a splurgenarf is. Can you give me a quick definition before I get started?”

“I’m going to just slop this incomplete code in and run it once to see the output. It won’t work but I want to see if the first part is on the right track.”

“I think you’re asking me to write a wrapper around a basic network call so that it will _______. Is that right?”

Oh, and you’ll always home your first interview if it’s been a few years. Don’t sweat it, and don’t make your first interview at a place you really really want to work because of that. You need to go through a couple of interviews before your brain remembers how to function in a coding interview because it’s so far divorced from how a developer usually works.