Well, like the rules say:
- A link to the page on itch.io
- A quick summary of the game
- At least one embedded image or video
Put the link at the end, keep the summary at 3 sentences or shorter (if at all possible), pick out a screenshot that shows of the core mechanic of the game (an animated screenshot will work best). (Videos might work better for some users but personally, I prefer animated images or stills.)
There is also something I see on almost a daily basis, so I think it’s worth mentioning even though it should be obvious: A “release announcement” can only happen once in a game’s lifespan - on release. Some developers treat the Release Announcements as if it was created exclusively for their personal use and just spam announcements for games they already had announced before. Imagine what that place would look like if everybody did that… :/
And something else I see every now and then: Announcements for a prototype, a “first glimpse”, a demo, an alpha, a beta, a pre-release, a pre-order, and whatnot. If the game actually comes out it will get less attention because users think they have already seen the game, even if it got improved drastically. While I don’t think developers break the rules by using their one shot for a release announcement for an unfinished game, I feel like what they would actually be looking for in most cases is feedback. Which they could have gotten in Get Feedback.
That’s about all that comes to mind right now. Hope this helps you and maybe others.