Lets start from the ground up! Your deck needs to sit on something. There are a few different options:
Concrete Piers / Sonotubes
Using concrete is the most common option for a deck foundation. It provides more structural integrity compared to deck blocks which are not ideal long term with our climate. It entails either using an excavator or auger to dig down 4ft and install a concrete pier for the deck to sit on. 4ft deep ensures the frost won't heave the piers.
This is becoming a more and more popular option. Its benefits outweigh those of concrete piers and deck blocks. There's also less mess and higher accuracy with positioning. A machine drives the pile, which is a really big screw, into the ground between 7-15ft depending on soil contents. The downside is they are the most expensive option, becoming more on par with concrete piers for large decks.
The deck block option is for those who are trying to keep the price low. While not usually recommended it can serve its purpose for ground level decks. Typically over time the deck will start to settle or heave in places. For install, digging a small 1ft deep hole with a machine or by hand and installing a small concrete base placing the deck block on top then backfilling the hole.