How to properly train a Rottie/GSP Mix puppy?

Our puppy is a male and is 8 weeks old (2 months). He weighs 14-15 pounds and we've already started to train him on how to sit and lay down. I've been warned a lot of times that his breed needs to be trained properly otherwise he will grow up to be aggressive, etc. I also need some tips on how to make sure he knows we are "on top of his pack"? More tips and advice is appreciated!

Put him in a puppy training class. Even something like Petsmart. They teach you about how to train them and how to be the leader. But some little tips:He should be sitting calmly before you give him any attention.He should be sitting calmly before you pet him.He should be sitting calmly before you play with him.He should sit and stay with the door wide open, while you walk out first. He can then be released with an "okay".He should sit and stay while you prepare and put his food down. He can then be released.You should not rough house play with him.He should not be allowed to nibble. If he does, immediately stop giving him attention. If he continues, give him a timeout in a relatively small room for a minute.He should be on a feeding, walking, and playing schedule.You should always eat first.You should always walk out and in before him.You should be the leader when walking him. Don't allow him to run out in front of you. Simply stop when he pulls, and only continue walking when you have his full attention.Oh and get him as socialized as possible!