oh boy - building a smoker!!!!
If you know others that smoke - take a look at their houses and see what they like and don't like about... if you are doing cinder block or brick - I would suggest mock building it (without mortar) so you can an idea for the size... and also ideas for where you want the racks to go and how you can customize it.
We had tons of ideas - (everything from hook hangers throughout to chains suspended from the ceiling down the sides) but ended up using rebar that would stick out into the smoker a couple inches. From the metal rebar sticking out of the walls - we could attach rods for hanging sticks - or put a length of wood down the rebar so we could better support racks for food to sit on.
My buddies uncle had a very simple cinder block smoke house with a tin roof and ??? for a door. I think it was an old house door that happened to have a piece of tin or some other metal on the interior side.
We built one similar to that out at my uncles farm - It was incredibly hard to keep the temperature at my buddies uncles - so we adjusted by making it a little taller so we could putting a half cut barrel over the fire pit and putting in adjustable vents (at the top and the bottom to control air flow better) I think we actually took the flat floor vents out of his house!!! It was a trial and error for sure.
great design here - http://www.meatsandsausages.com/smokehouse-plans
My uncles land has a lot of lumber available and he happens to have some wood working tools so we'll be looking to add one of these - http://www.goodshomedesign.com/how-to-build-a-smokehouse/
This site has quite a few ideas too - http://theselfsufficientliving.com/12-smokehouse-plans-for-diy-smoking-food/
Bigger is not always better!!! Take into account how much product you are going to be smoking - what product you are going to be smoking - does it need to look professional (if you're in a community) or doesn't it matter as long as its functional - and options for further expansion/adjustment/customization of the smoker.