Brick fire pit

So i just found this site today, and am very glad about that. However when I attempted to search the archives regarding a back yard brick firepit, I only found other posting the same questions with no answers. I also cross posted this on the fix it board

I did find this one site that provides an example of how to do it.. http://www.livinghome.com/news/gardens/178-1.html

However it does not answer my other questions.

Do I need to use a special type of mortar?

If I would like it to be higher than say 18" do I need to provide some type of ventilation

any other suggestions or comments greatly appreciated also feel free to email me if you prefer. thank you,

Mike