Spot o Bedlambeast! (Hey, that user name describes my GSD perfectly!)
Also lots of socialisation - there's nothing more distressing to dog or ownner than a dog which is dog aggressive and needs 100% watching/100% lead walking, gets into fights, goes mad at the sight of other dogs and causes rows with other dog owners because he hasn't had plenty of opportunity to be socialised from an early age. I see too many such dogs coming into rescue like this and they suffer in many ways though it isn't their fault.
Add to that neutering, for similar reasons.
Stairgates if necessary, maybe a crate for short periods of time when you are out and he is still chewing/peeing on carpets.
Firm but gentle setting of boundaries, consistantly. If you don't want your guests to have hairy bums when they get up from your sofa when they make to leave, as mine do, the ensure that you lay that rule down from day one, you stick to it and even your soppiest child does too.
Patience, love and the realisatio that I am extremely jealous!