[The Newell]

Never use concrete blocks, or masonry, as they can crack or crumble.
Block it up using the jack points on the newell, or drive up on ramps, or over a pit.

make sure the footprint of the blocking is large enough. a newell is heavy enough to drive a 20 ton jack into asphalt or dirt, thereby lowering the coach.
Be aware of how low the newell can go or how far it can fall.

I drove mine up on wooden ramps. Even if the bags are fully deflated, there is still room for me under there.
railroad ties are good, as long as they are not cracked. Wood can still split and fail, and a newell has the weight to do it.