Unfortunately, there's no single place where all of these instructions are localized. That definitely should be done at some time.
I've posted a couple of threads in the Plant Database Forum that might be useful to you:
The thread "Common errors in new plant proposals" in
Plant Database forum
The thread "Common errors in data proposals" in
Plant Database forum
You're right, of course, that all of these instructional threads should be grouped together somewhere, but I want to assure you that the admins are not "burdened" by the mistakes members make. We're here to help you. If a member is submitting lots of proposals or photos and getting something wrong, we usually point out the errors to the member, and then we don't have to correct anything after that. In most cases, people submit just one or two proposals requiring correction, and that can't be considered a burden by anyone.
The main thing, though, is that everyone here is eager and willing to answer questions. If you're not sure about something, start a thread in the Ask a Question Forum, Plant Database Forum, or Site Talk Forum. People will be happy to answer your questions.
