What should I look out for when doing my deck choice of timber?

Timber should be of specific moisture content to suit your local environment. Local authorities can inform you of this information.
Kiln Drying – Provides consistency, Stabilises the timber, Reduces twisting. When a supplier goes to the trouble of kiln drying your timber it is more expensive, but the end result is well worth the cost.
Only use timbers that are Durability class 1 and 2.