A lot of people have already given great advice!
I am assuming you have a puppy. I have very little puppy experience. The dogs I have fostered or adopted have typically been between the ages of 7 months to 6 years – although I have fostered 6 week old orphans and 9+ year old seniors too.
With that said, I believe the single most important thing you need to work on before anything else is positive engagement with the dog (no matter the age). As others have said, building focus is an important piece of that, but make it fun… be the most positive and interesting thing in your dog’s life… learn what motivates and encourages your dog. In so doing, you will find that your dog will also start to learn what motivates you... lol!
Once you have established a positive relationship with the dog, the rest comes a lot easier. So, in my opinion, the focus of early training should be on building a foundation of mutual understanding and trust.