A few points to add to this:

Crossposting
If you're going to post a thread, once is enough.
Placing the identical thread in multiple locations, known as crossposting, is frowned upon.
Just take the time to place your thread once... in the best suited forum and wait for a reply.
If you feel that your thread would be better suited in another sub-forum, don't crosspost/repost it... just contact a member of the staff to have them move it for you.


Thread bumping
Thread bumping is when a person posts a short note to "bump" their thread to the top of the forum.
While it isn't necessarily a bad thing, it is an annoyance when the OP hasn't waited at least 24 hours of no response before doing so.

Keep in mind that this is a forum and not an instant messaging service.
It can take time for someone to reply to your thread, so just be patient.
If more than 24 hours have passed, maybe a little bump is okay... but just give it time.


Double posting
Double posting is when you post your response, but then immediately post another reply after it.
This may be done because you have forgotten some information or perhaps you are addressing a reply that came while you were composing your post.

Now, if it's been a day or so, then it's not so bad.
However, if it's only been an hour or even mere minutes then there's no need to double post, since you have the ability to edit your posts.

So, instead of adding another post, just click on the "Edit" button and you can add information to your existing post.