dig the area out that you are going to deck,level the area put down a weed barrier layer (a black material for stopping weeds growing through)put either sharp sand or pea gravel down and level it ,then make your base using treated 4by2 beams nailed together,then screw your decking planks or tiles on top using non rusting screws,it helps to treat everything with stain or paint as youre putting it together oh and try to pick a cheap stain or colour i picked lavender stain at �14 and could have bought a new house by the time i finished painting!good luck