It depends upon the amount of weight you are supporting. I have found around here that decks and fences with cedar and redwood posts buried in the ground are rotting at ground level over time. I've changed my thinking and will make a deck using just posts on concrete blocks or piers on the ground if they aren't very big, heavy, high. I quit attaching them to houses to. If it takes much weight, then I'd use a reinforced concrete pier(formed with round cardboard forms or just poured in a round hole) down to the frost level to avoid frost heave. Then put your posts on top of the piers in one the metal post bases you can buy. Can't do that with fence posts though.
In your situation, keep the cedar pier off the ground or if you go the other route, pour the pad for your concrete blocks down to frost level. Not easy digging but better in the long run. Best route may be to jack the house up a little higher than what it needs, dig a 8" bell shaped hole down to frost level. Then use a round cardboard tube form to finish out up to the proper height. Use rebar throughout. Do it in one pour if there is room or at least pour it to ground level first and then do a second pour for the tube.
Around here they have the bad habit of setting mobile homes and double wides with a flat concrete pad right on the ground with blocks above it. Which is basically what I'm doing now for small decks but mobile homes are too heavy. I know of one I need to relevel one of these days and it won't be fun crawling around with jacks.
If you need shims, have some cut as wide as the beams from oak. The cheap cedar shims you buy will just smash flat after a while with something like a mobile home on them. Then your back underneath again.