Staging Area, copy tables

Right now, I am dropping tables and creating them as select ...(whatever I want). I am doing it to get to the transformation part asap, but I really have doubts about this. I could trunc(table) but then what if the structure changes? So, I am just trying to figure out the best method. I am using oracle warehouse builder, and what I am assuming might be best is to create staging mappings, that will just be a 1 to 1 copy. The downside to this is that I would have to create each staging table to extract to, but it would allow syncing of them if the source table changes. I am curious as to what you think?