Let's see, some that I consider the most helpfull....
If down in space, trade pieces, not pawns. (and vice versa).
Develop knights before bishops, and queen last of all. You need to see what develops before you know where the bishops and queen belong.
Rooks belong on open files, and behind passed pawns, and on the 7th rank if possible.
Oh, and of course, e4. Best by test! 
Play the position. Period. If you are involved in an open or semi-open game where tactics will rule the roost, play that way. If the game is closed and more of a positional struggle, play that way.
The position will tell you all you need, if you can recognize what it's saying. :)
I see... Could it be a maxim that helps me recognize what the position is saying?
"Weak points or holes in the opponent's position, most be occupied by pieces, not pawns."... Siegbert Tarrasch
"An attack on a wing should be met with play in the center."... Nimzovich
"The scheme of a game is played on positional lines; the decision of it, as a rule, is effected by combinations."... Reti
"Strategy requires thought, tactics require observation."... Max Euwe
"Tactics is knowing what to do, when there is something to do; Strategy is knowing what to do, when there is nothing to do."... Savielly Tartakower
"When you see a good move, look for a better one" - Emanuel Lasker
Einstein said once - I'm not very sure and this maxim can be applied to everything in live- i hope.
OK here it is: Logic will take to you from A to B and imagination will take you anywhere.
Here's one from my GM teacher: The board is wider than it is tall.
Bonus points to the first person who gets the point.
Always assume that your opponent will make the best move possible.
This prevents a lot of "well maybe he won't see it so I'll just try it anyway" situations that often backfire horribly.
The other side of the coin is, after your opponent moves, figure out what he did wrong. ;)
Ozzie - is the point "don't overextend your position"?
It is always better to sacrifice your opponent's men." - Savielly Tartakower
“One doesn't have to play well, it's enough to play better than your opponent” Siegbert Tarrasch
Here's one from my GM teacher: The board is wider than it is tall.
Bonus points to the first person who gets the point.
does it have to do with playing the full width? not sure I understand
Is 11 years some sort of record on here for replying to a post ?
A Knight on the rim, is grim.
"Amberley excelled at chess. One mark, Watson, of a scheming mind!"
Sherlock Holmes aka Sir Arthur Conan Doyle, The Adventure of the Retired Colourman.
Is 11 years some sort of record on here for replying to a post ?
oh my god i didnt even realize
Do you have a favorite Chess Axiom or Maxim?
Maybe one that has helped guide some of your moves.
Perhaps an epiphone that improved your play.
One of my favorites is:
Axiom 1: Knights are slower than Bishops. Axiom 2: A positional move should maximize the gain in activity. Rule: Move Knights before Bishops in the opening. Prove: A fast piece on his home square is better than a slow piece on his home square, therefore, a Knight gains more activity with his first move than a Bishop...
Please share if you can :)