There is an official Community Guidelines thread, and a Quick Introduction for New Users, and more recently an official Users Guideline put out by NI, but I feel it isn't as complete as it should be. So here is the list of unofficial forum rules. These are community sourced guidelines and new users can be pointed here, if they are unsure how forum etiquette works. These guidelines are focused on the LabVIEW forums, but most of the suggestions apply to all NI forums.
Before Posting a Question
Many posts have been made on the forums over the years and many topics have been covered. You are likely not the first person to attempt something, or having difficulty. Search the forums first for the question you would like to ask. NI's forum search works well but feel free to use Google to search the forums. Try searching with alternate terms, like "System Tray" instead of "Icon Tray".
Posting a Question
When posting a question you should first follow the guidelines linked earlier. Ben on the forums has a good quote which is "The first step in solving a problem is clearly defining what the problem is." In addition to those points I'd like to mention a few more:
When Posting Code
When you don't get the help you want
If you posted a question and didn't get any response, or didn't understand the responses you got, do not make a new thread on the same topic. Doing this will fragment the conversation and you will have two groups of people working on the same problem.
Don't simply BUMP a thread with a new post without more information. This is a sign that you don't want to put in any effort and are simply nagging others to help you. If a thread goes dry and you want more help, try getting more information on the subject, or try something and reply to the thread with this new information. This shows you are willing to work towards your goal, and aren't just looking for others to do your work for you.
When you get the help you want
Volunteers put in effort to help you and they want to know they are appreciated. The forums have several ways to say "Thank You" to those that have helped. More information can be found on NI's official Recognition and Ranks topic. Here are the preferred methods.
Things Not To Do
Looking For Free Training
Many times new users of NI hardware or software just don't know where to start. They will ask a question but without knowing the terms, or the intended purpose, they will not be able to form a proper question. Here are some free training tools primarily focused on LabVIEW and NI hardware to help get started.
-MyRIO Project Essentials Guide (lots of good simple circuits with links to youtube demonstrations)
The best way to learn, is to follow the tutorials, then ask lots of questions.
Beyond the Training
People take training for various reasons, but one of them is be proficient enough to get recognition for their experience. This can come in many forms, but the easiest to put on a resume is a certification. LabVIEW has three basic levels of certification, the first is the CLAD, the second is CLD and the last is the CLA. Each of these have their own specific challenges but useful user experiences for each of these are discussed in these Certification Nugget threads.
The original discussion for this document started here. Feel free to add comments below of suggestions. This document should be updated periodically.