Flattening Ground for Beginners

[Catote]

Next on my list is building a mine. The game refuses this.
First because the ground wasn't enough paved. Now the whole area is paved.
Now the game just refuses to build the mine with no error message.
I assume it's because the ground is not flat enough. So hence my question: for beginners: how do I go about flattening the ground.

Obviously I can dig dirt. And with some right and left clicking I can drop dirt. Either one drop, level all corners or drop all.
BUT I have serious problems seeing where there is a corner. Where there even is a tile, so it doesn't really work for me.
I'm using Latika's client. Does that even work with flattening ground?
I see some nice pictures in forum where other people can see a grid, and info about ground highs in the grid. I have no such thing.

Tips are much appreciated, thanks.

[Kandarim]

press ctrl+L to bring up flattening help, select a piece of ground, press ctrl+L again to ungrab the mouse pointer. (ctrl+F works as well). Works in both Ender's and mine.

It'll give you a grid: red is highest, blue is lowest, as well as the height difference between the highest and lowest.
ctrl+clicking a tile when in digging mode will flatten that tile, and shift-rightclicking a tile when carrying dirt will raise all of the corners to the height of the highest one (I'm not 100% positive on the ctrl/shift modifiers here, they might be reversed or something, but they exist )

[TemplarKnight]

Next on my list is building a mine. The game refuses this.
First because the ground wasn't enough paved. Now the whole area is paved.
Now the game just refuses to build the mine with no error message.

could also be that you are not prospecting while placing the mine sign.you have to have a woowoo wand(or rods) and be prospecting to be able to place a mine entrance.

[Catote]

press ctrl+L to bring up flattening help, select a piece of ground, press ctrl+L again to ungrab the mouse pointer. (ctrl+F works as well). Works in both Ender's and mine.

It'll give you a grid: red is highest, blue is lowest, as well as the height difference between the highest and lowest.
ctrl+clicking a tile when in digging mode will flatten that tile, and shift-rightclicking a tile when carrying dirt will raise all of the corners to the height of the highest one (I'm not 100% positive on the ctrl/shift modifiers here, they might be reversed or something, but they exist )

Thanks. I flattened a 5x5 grind and managed to place a mine building spot. Also I managed to put all stone/boards/bricks into it, before the game crashed today, and now it's all gone. Thanks god, it wasn't my only 8 nails I lost there ...