Some places to find blueprints for building a smoker include Popular Mechanics and SmokerPlans.net. Both of these are available online, and the one from Popular Mechanics is free as of 2016.
On the Popular Mechanics website, PopularMechanics.com, there is a link to a PDF blueprint of a smoker. The finished smoker weighs around 100 pounds, but with two handles, the smoker is easy for two people to move around.
At SmokerPlans.net, there are more than 100 blueprints for smokers. Some of the blueprints require propane as a fuel source while others require oil. There are cabinet style smokers and horizontal ones. Many of the plans are just variations based on the weight of the fuel source.