Screenshots: Why would it be a good idea? Because if you want people intrested in your game / tool add this before uploading your project.

Uploading your projects files: .zip, .7z and .rar are reccomended because, that it contains the files of your game / tool.

Want to add? Comment below of this topic to add to this.

Don't forget cover art, without it your game won't even show up in searches. And please don't use .rar files, it's a proprietary format that's a hassle for people to deal with.