Here's a few tips.

To create a new LD account (if you don't have one yet) you will need an invite code, this is posted on the LD twitter (and other socials) for the upcoming jam. https://x.com/ludumdare/status/1827812733523230866

New accounts will be "untrusted" by default, make an initial post to the feed (such as introducing yourself, listing what tools you'll be using). Your post won't be viewable on main but will be viewable on https://ldjam.com/feed/raw Posting helps your account be manually flagged as trusted at some point. All these steps are to help deal with the large number of spam accounts.

Don't worry about joining the jam or getting your entire team setup on your game page before the jam starts, you can do this at anytime before the end of the jam (but obviously don't wait until the last second).

To add teammates to your game, make sure you follow them and they follow you, then you will see them in the Author(s) dropdown box when editing your Unpublished Game.

The theme slaughter and voting rounds don't have specific start dates and the number of voting rounds has been different in the past. You do not need to go through all themes in the slaughter round, everyone doing some is enough for it to work. Word of warning, don't become too attached to a theme during voting rounds.

Reading this once or twice will help: https://ldjam.com/events/ludum-dare/rules

The rules are probably a little out of date. There are 3 categories, not 2. Compo (solo 48h), Jam (team 72h), Extra (2 weeks). More info about Extra here: https://ldjam.com/events/ludum-dare/50/$276398/extra-the-new-casual-ludum-dare-format

AI usage guidelines: https://ludumdare.com/resources/questions/can-i-use-ai/

If anything above is wrong (I'm relying on past info) or have other advice, please reply to this post.