[Discussion] Tips for dog walking

I have a 6 month old Golden Retriever who I need some advice in regards to when he is being walked.

While on the lead he will often do his best to walk as far in front of me as possible, continuously pulling on the lead. He is not aggressively pulling, but it's constant tension as if he wants to walk faster and away from me. He will still do this when I have the lead extremely short and he is next to me. He will continue pulling until we have been walking for a long time and he gets tired and then he is fine. Is there any way for him to relax from the beginning of the walk?

Also, I am trying to train him off lead for when we are at a park. He is very hit and miss as when there are no distractions he will go and sniff as he pleases and return to me when I call him (this may take 2-3 tries). However, when he see's another dog, person or occasionally a bird, he will run as fast as he can after it, and no matter how many times I tell him no, or to come back to me, he will stay with whatever he's running after until I pull him away. How can I fix this?

I understand that this could be due to him only being 6 months old, but I am after some guidance on how to stop unwanted behaviour as early as possible. Any advice is appreciated.