Workflow questions for someone starting out...

Hey,

I have a few questions about workflow as a few things are timing consuming when I think there are probably quicker ways of doing things (especially after watching so many tutorials online and how quick some people are with key commands).

Firstly I am wondering about snap. I have gone into Snap Settings. I've put everything down to 0.1. Then when using the Cmd (on a Mac) key, I can't seem to snap anything (prefabs and buildings).
When I create a cube, transform it into a wall shape and then copy and paste a duplicate followed by rotating it 90 degrees to create a right angled wall, I can never seem to have it lock onto the other piece of wall.

Another thing about snapping is when I drag a prefab into the terrain, how do I move something and have it snap straight to the terrain, or a plane?

Looking around

So holding Alt is a Key command for look around and the QWERTY keys are the shortcuts. That's great but navigating around is sometimes a bit of a pain. Is there a way of double clicking on the Terrain and like pressing the F key on an Object, anyway to zoom into to where you double click (perhaps that's just playing too many games thinking that's possible?).

Also, let's just say that I've been building an area, and then I want to place a building quite far away from where I've been building. Is there a way of moving your playable character so when you want to test the game in play mode, you can just appear there or do you have to manually move your playable character/camera to where you want to appear?
Just trying to grasp these basics!

Many thanks for any help

Jono