The Xacto #11 blade and the single edge razor blades are both used for self-inflicted blood tests (couldn't resist)

Actually I use single edge blades more than hobby knives when cutting out parts, making long pieces shorter and for cutting covering.

Get a good straight edge (metal preferable)

Sanding blocks can be as simple as a block of hard wood with sandpaper stapled around it. I use 60 grit, 100 grit and 220 grit.

Above all, get a warp-free building surface to minimize the built-in warps in your model of choice.