I had used 3D before. Blender still started me from zero.
I had used 3D software before. But the program I knew had its own way of thinking about space, and its own way of controlling it. In Blender I had to go back to the very basics. Everything below looks obvious to me now. On that day, all of it was new.
On my first day I was stuck with the default cube. I didn't even know how to move it.
1 · To move it, press G
Just to move the cube I had to learn that the hand is on the keyboard, not on a button. G moves. R rotates. S scales.
2 · Front, Side, Top, and which way is up
I had to relearn what Front, Side and Top mean here, and which axis is which. Z is up.
3 · Perspective or Orthographic
Draw and measure in Orthographic. Look in Perspective.
4 · The view turns around a point. Pick the point.
Orbiting and panning used to be muscle memory. Here I had to build it again. Sometimes one turn and the object was gone from the screen, and I didn't know what I was turning around.
5 · Object Mode, Edit Mode
When I first made something in Edit Mode, the new geometry became part of the same object. I didn't yet know that Object Mode is for things, and Edit Mode is for the points, edges and faces inside one thing. So everything was stuck together, and I was even more lost trying to pull it apart.
6 · Pulling it apart
Select the part, press P, choose Selection. It becomes its own object.
The habit I kept was from school: draw a line, give it a size, push a face.
The tools I make sit on that habit, inside Blender's Edit Mode. Axonobox, on the objects page.