Making a model
All the action happens in my garden shed
I research the chosen item, looking at pictures of real items on the web and obtain overall measurements of examples. From this I can estimate additional measurements by scaling pictures to the known sizes. Fortunately, scaling down to 1/12 also means that errors in measurement are also reduced (visually, at least). Using these I draw 1/12 scale drawings of the item from sides, top and bottom. This means that when pieces are cut and assembled they can be matched to the drawing to maintain accuracy.
Assembly process
Often it is useful to make a template or jig to support the assembly. I use Gorilla wood glue mostly, as it allows time to position the pieces before firming up after a few minutes. At certain stages I wait until the next day to continue as this gives the glue time to harden.