I'm going to see if I can get David to do a screen shot for demonstration purposes (MOD EDIT: Done ) but I wanted to walk those of you out there that accidentally post double about how to delete and edit your posts in a thread. First, when viewing your post in a thread at the bottom of your post there are 4 little boxes at the bottom of the posted box. There is; Edit Post, Reply, Reply With Quote and Quotes (this one is if you would like to do multiple quotes in a single post). To Edit or Delete, click on the Edit box.
Next, a screen will come up with 4 new boxes at the bottom; Save, Go Advanced, Delete or Cancel. You will want to Edit your post at this time within the text box if you would like to Edit it and then click on Save. You may or may not want to add a reason for editing, that is up to you.
If you would like to Delete your post because of an accidental double post, you would click in the circle next to Delete Message and then click on the Delete Post Box at the bottom right. Viola, post deleted. This method of edit and delete works on just about all forums with this type of system.
One Post Script: If in fact you post a double Thread, the only way I know of to delete one of them is to have a Moderator remove it or join it to the other thread. In these cases, send a Private Massage to one of the Moderators.