vi file.txt
vim file.txt

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gg     goes to top of file. NNgg goes to line NN. NN means an integer OK?
G      goes to bottom of file
dd     deletes current line under cursor. NNdd deletes NN lines
yy     'yanks' ie copies the current line and NNyy yanks NN lines.
p      pastes the current buffer at the end of the line the cursor is on. 
       Both dd and yy fill the buffer.
^      goes to begining of line like REs. Literal ^ not control BTW
$      goes to end of line like REs
u      undo, NNu undo last NN changes.
Ctrl+r redo, NNCtrl+r redo last NN undo-s
x      deletes char under cursor. NNx deletes NN chars to RHS of cursor.
r      type r and the next char you type will replace the char under the cursor. 
       handy for s/'/"/ and the like.
J      Joins the cursor line to the line below ie remove \n from cur line.
       Note j is nav J is join.....

Note Backspace will more you backwards (ie navigates but no deletion in nav mode) but 
DEL deletes as normal (ie no navigation stuff disappears). GOK.

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:w     writes file
:w!    writes file even if read only
:q     quit
:q!    quit and don't mess with me. ie if I have made changes 
       ignore them and exit with no write (good for f ups)
:wq    write quit (usually what you want)
:wq!   write quit don't question my wisdom!

There are also lots of neatish widgets, here's three

:shell       gives you a shell to do stuff. type exit to return to vi.
:!command    gives you a shell immediately below colon.
             ie !./script while you are editing 'script' it will exec it.
             hit enter to return to vi as prompted, else type more commands.....
:%perldo s/this/that/   execs that perl s///

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a     Insert after the current cursor pos 
A     Insert after the end of current line
i     Insert before the current cursor pos
I     Insert at the begining of the current line