The main decision is what material to use. Years ago there was only regular wood (spruce or hemlock) and from there it progressed to pressure treated, which is treated southern yellow pine. There are many more choices today. The most popular is Composite or PVC decking. There is also composite decking with a plastic wrap which helps with preventing mildew.
Generally, the customer will have some sort of plan or drawing of the deck they wish to purchase. We will estimate the quantity and lengths of the boards they will need to complete their deck. We do the same for railings if needed. The most popular is vinyl railing with little or no maintenance.
The biggest challenge is having the right plan and to make sure it is built to local building codes.
Regular maintenance for wood decks would be power washing, cleaning and re-staining. Maintenance for composite or PVC is pretty much just power washing or cleaning if there are stains or mildew.
I would suggest hiring a reputable and capable contractor for the above mentioned reasons. They will also be able to offer different ideas and suggestions.