Welcome!
Off the top of my head, a few suggestions:
- Familiarize yourself with a development workflow ahead of time. For small projects, the web-based version of Octo is very easy to dive into. For a bigger project, you might want to try c-octo, which can be used from the command line in combination with your favorite code editor. The Octo github page has links to community-created Octo syntax highlighting profiles for Sublime, Emacs, Vim, Atom, and VSCode.
- Try making something really simple as a warmup before the jam, like moving some shapes around on the screen.
- There are a bunch of programming tips, tricks, and hazards to avoid in the Octo FAQ- I'd recommend giving it a read.
- Don't wait until the last minute to submit! Putting together a nice itch page for your game can take some time, and it's no fun spending the final hours of October 31st in a panic. Posting a rough WIP earlier on can save you some serious stress and allow you to get valuable feedback from players before the final submission date. If you completely finish your idea with plenty of time left on the clock, you can always starting tinkering with a second submission...