For this tactic you will need 14 scvs on minerals and 4 per gas mound,but first deal with the minerals.Build three supply depos or more to block up your entrance(ON BGH)/exit.Behind that build as many bunkers right behind the depos as you can fit,and fill them up to the limit.After you do that start working on gas.Get four for each of your gas mounds then build two factories.Put about six tanks behind your bunkers and put them in siege mode.This should prove as a sufficient enough ground defence.Then get two-six starports(Do all of this while building extra supply depos).Upgrade the two Wraith abilities at the control tower and then start building as many wraithes possible.Each time you have 10,attack.Go behind enemy defences(along the side of the map)to their mineral deposit area and blow away their scvs/probes/drones and comand center/hatchery/nexus away.If this doesn't work build a science facility and go either battle cruisers or nukes.

CreepColony's Opinion: This is a very common strategy, especially in the "fastest" maps since after your town center is destroyed, you can't rebuild it (too close to resources). Usually though, people attack with around 24 wraiths.