Steve has already addressed the shrinkage we expect from TL. When wrapping a post, you need dry lumber that is sized. For deck boards, railing and trim we also know screws offer more holding power than nails. For trim boards, finish screws (small headed) are preferred. All screws should be galvanized. Also caulking the seams of the trim can help keep moisture from getting between the post and the trim. If the deck will be stained or left natural you can use a clear silicon caulk.
If you don't have time to do it right the first time, when will you have time to do it over?