Size, in this case, does matter, and it pays to be aware that whatever size you make it, it's likely that within a few weeks you'll be wishing it were bigger.
So give careful thought to how the deck is to be used. If it's going to be an entertaining area, factor in space for a barbecue, preparation and cooking facilities, a tableand chairs to accommodate the number of guests you usually have, standing space for people to gather for pre-dinner drinks, and space for planter boxes, container plants, pots of herbs and other decorative elements.
You may also want to factor in space for an outdoor fire, brazier or patio heater.
Keep in mind that if you have a large expanse of deck it's likely to look a bit boring. It's easy enough to introduce a second material, so if you've chosen man-made decking and want to add a more rustic element use a rustic timber as edging, or to divide your deck into different areas.
Channels of stones or plants incorporated into the decking will create interest, and you can leave cut-outs for existing trees or plants.
Before you so much as lift a spade or hammer, consult the local council to check the regulations.
Safety features such as handrails will be required, there may be boundary restrictions, and you will almost certainly need a consent.
The exception to some of these limitations is if you want a freestanding deck. Although we are more accustomed to decks that are part of the house, decks are more and more often being used as separate spaces within the garden.
A deck that's virtually flat on the ground can be used to provide a sitting space near a focal point of the garden, or simply to enhance a landscape design.
Of course, you can't simply plonk a deck in the middle of the grass and leave it at that. If it isn't attached to a building you need to provide edges and borders that will give the sense of enclosure you'd otherwise borrow from the house or the wall.
Substantial rocks that are from 60cm to 90cm high are fantastic for this. They anchor any structure or garden design and give it a reason for being.
They also create boundaries, provide focal points and can be arranged to give you pockets to plant in or a backdrop to plant against.
Another great advantage of a deck flat on the ground is that your plants don't have to be very big to make an impact, so you're not going to be waiting till next spring for it to look good.
Choose a couple that are a decent size to give it an established look, and fill in the gaps with smaller ones.
Add a couple of stylish chairs, a table big enough for a book and sunglasses and you're done.