Probably the most fun aspect of using adobe is building arches. These make great door and window openings. And they the surprisingly strong and can bear a lot of weight. First, build a wooden form and support it at the level you want to start the arch. Then as you build arch the form, use a string attached to the center point to keep track of each brick's alignment.
You can also use stuffed bags to build a form.
In the case of our largest arch, that worked just fine!
Testing them out once they are dry is so much fun!