New here, just got the ability to post; is there anything I should be aware of that newbies usually miss and/or forget?

https://e621.net/wiki/show/avoid_posting
https://e621.net/wiki/show/howto:sites_and_sources
https://e621.net/wiki/show/e621:tagging_checklist

Although it's not needed, ask for permission before posting anything that isn't yours. This includes the artists(people who'd drawn), commissioners(people who'd paid), and the character owners(people whose characters are involved).

Find the best resolution for the artwork you're posting. Don't post any low quality, IRL, DNP, commercial, or irrelevant content.

Tag properly and accordingly. Based on what you see and not what you know*. This is to ensure that people get what they'd searched for and/or blacklisted.
*^{There're exceptions for technical tags (like artist, year, resolution tags).}

Please source your stuff and give some credit where it is due. A single direct-link to the image itself (or even no links at all) would not help people who're trying to find the artist and/or the original post.

Rate correctly. I don't know why but a lot of people get into trouble on this last step.