How do I move blocks or align them? Difficult to start a new small grid

I am still new to this game. I am trying to build my first small grid from scratch. I am finding it very difficult. I start placing blocks and the grid may tilt. How do I straighten it again? I want to place a block under another block and below my eye level. I won't snap under the block. How do I place it? Take landing gear for example. I can pl;ace one but how do I place the other if I can't have it snap under blocks.

Can we pick up blocks? Can we move or push blocks? I read hit "F". That doesn't work. Hit "J". Nope. I read there was a key to change to build mode. Not that I find. I can click to place a block and it goes into build mode but that is only to place a new block.

Having a lot of trouble....

 

1. Start off with putting a temporary landing gear on ground. If you weld it, it will be locked to ground automatically, so regardless of what you add later it will not tilt or move. I usually start with that, build few temporary light armor blocks up (to have clearance to attach wheels/landing gear or work on the bottom) and then start actual vehicle I want to build. Then at the end I grind down the temporary blocks to end up with exactly the vehicle I wanted.
2. You have to aim at block surface to have new block be attached to it, so if you want to put something below your line of sight, there are only 2 options: a) crouch (if it is enough) to lower your viewpoint, b) use jetpack and flip yourself upside down - this way you can basically scrape ground with your head upside down, so you can see the bottom of basically anything not lying on the ground directly.

Unfortunately there is no option to pick up blocks by hand. To do that you would have to use vehicle with extra landing gear that can "grab" grids by attaching to them.
On foot, the best you can do is walk into them to push them, but it hardly ever works as smooth as you would like it to.

 

If you run through the tutorial missions that should give you a good idea of the game mechanics and how it works.

 

I'm assuming you're on a planet with gravity.

Place some large grid armor blocks down to make a pad.
Next, switch to small grid armor blocks and create a stand for your small grid vehicle sitting on top of the large grid blocks. I typically make a cross or a "T".

Then I build my small grid above the stand. When I'm done, I just grind away the stand carefully after powering up the small grid vehicle.

 

If you're building in free space and you bump a grid, it will have a tendency to move. Once moving you will not be able to stop it with just your suit. Things don't get "stable" until your grid has power, gyros, and thrust in all directions.

Having external power and a solid anchor point to build off of makes things a lot easier.

I usually do my scratch building off a station (large grid); build a rotor, remove the large head, add a small head, and, as Ronin mentioned, build a sprue to give yourself enough space to get all the way around the new construction. You need to leave enough space to place blocks like landing gear so that they won't be touching the floor.

Note that large blocks can be placed into the ground and small blocks cannot. When building a large grid ship, make sure you don't build it into the ground.

Splitsie has some good tutorials: https://www.youtube.com/user/Splitsie

 

I place a pad of large blocks. Then a small landing gear. Build some armor blocks up from there, don't weld these, you'll cut them off when your done. Then build your craft/buggy/ship.
If on a planet you can put down a large slope for stairs to a large block (don't weld these) as a scaffold to have easy access. Later when you have lots of ice you can use you jets, but early game scaffolds save aggravation.