Step 1: Designing your pergola

The location of your pergola will affect the construction materials used. A rustic pole construction usually looks better at a distance, whereas one of planed timber is more fitting adjacent to a house.
If you use softwood, either buy pressure-treated or apply preservative yourself. Always apply extra preservative on cut ends.
The uprights should be at least 75x75mm (3x3in) wide and about 3m (10ft) long as they will need sinking 0.5 m (2ft) into the ground for adequate foundations. If you are placing the pergola on a firm concrete foundation, you could use metal fence bases which bolt through the concrete.
Your pergola can, if adjacent to a house, omit poles down the house side. The cross beams are then fixed directly to the wall using joist hangers, as illustrated.
If fixing on top of decking, you can either set the posts in the ground around the edge, or position through holes cut through the decking next to a joist. Use two offset coachbolts to attach the base of the posts to a sturdy joist for stability.
Your individual design may, if large, need additional supporting posts - every 2.5m (8ft) or so is about right.