To follow up on one of the points in Dapper Dan's SPAM guidelines (which I thought were helpful):
4. The double-post: Posting twice in a row, without good reason.
For those of you who are new to forums like this, one way to work with this type of situation is to edit your previous post if you have additional information to share. What I do is edit the post and add the letters
ETA: underneath my initial post, in a bold font like this or a different color, and then add whatever my additional text is. It prevents the double post, and you still get to make your point without having to wait until someone else posts in the forum
ETA: Just wanted to check on the actual mechanism to edit a post, which is the "Modify" button that is in the upper right hand of someone's post.