I will soon be pouring a 20' by 80' driveway. What is the best way to do this? Thinking of pouring 10'by 80' one day the repeating the next day for the other 10'. Do I need to pin the driveway to the garage floor and do I need to pin 10by 80 sections together to prevent uneven heaving? I am in the north. If so how? Thanks!

I would definitely not create an 80' long joint. Joints are potential problem areas and if it is just a matter of making smaller pours a transverse 20' long joint across the width is the same quantity of concrete, with one fourth the joint length. Longer reach for finishing but you can rent long handled finishing tools.
Expansion joints are only required where both ends of slabs are confined by fixed objects. It doesn't sound like you have that situation but if it were me, I would put expansion material (say 3/4") at the garage end at the construction joint (if you use one 20' joint across the width. I would only consider tieing the new driveway to the existing garage if I had a steep grade (falling away) from the garage down the driveway. I am assuming that you have a good solid base with stone.