The 1st RULE of Minecraft is: You do not dig straight down.
This is important. It has killed many miners, and lost many diamonds.
The 2nd RULE of Minecraft is: You DO NOT dig STRAIGHT DOWN.
If you didn't get it before, DON'T DIG IN A STRAIGHT LINE DOWN! MEMORIZE IT.
3rd RULE of Minecraft: Your best, fastest, and nearly infinite source of food is mushrooms.
Get the mushrooms, add bonemeal. harvest, cook, repeat.
4th RULE: You don't need a house to have shelter.
Do not be so proud as to have to build an intricate treehouse or mansion in order to pass the night. Nobody is judging your hole in the ground, that is your SAFE hole in the ground.
5th RULE: Carry a bucket of water. Always.
Elevators, Mob Pushers, lava killers. A Bucket of water is your friend.
6th RULE: A pickax can be just as effective as a sword.
Swing that stick and send that Creeper back to Herobrine. Axes, Picks, Shovels, Swords, they are all more effective than your fists.
7th RULE: Learn to strafe.
Skeletons are snipers. They will pop up out of no where, so learn to avoid their arrows.
And the 8th and final RULE: If you can't find your home base? Build another one.
Why? because then you'll have TWO cool castles in the sky instead of just one!