Minecraft Survival Tips
There are already a bunch of Minecraft survival tips scoured across the web, so I won't be covering all of them. Nonetheless, I decided to write down a few that I find are either essential, or that I didn't see anywhere else.
Your bed acts as spawn point
Most of you know this, but for those who don't: When you sleep, the spawn point gets changed from the original location to your bed! Thus, when you die, instead of respawning in some faraway land, you appear in the comfort of your home.
Mine in the "Extreme Hills" biome
The subterranean minecraft world is huge and full of resources. That being said, you should concentrate your mining in the "Extreme Hills" biome, since it is the only one spawn emerald ore, which can then be exchanged with villagers for goods, or used to craft emerald blocks (which are beautiful for building).
To find out what biome you're in, press F3. The current biome is shown near the bottom (I have a texture pack installed, but it's at the same place in default Minecraft):
Breed cows instead of pigs
There's really no advantage to breed pigs over cows, they require both the exact same quantity of wheat in order to reproduce, and cooked pork chop restores the same amount of hunger as does steak. So in those regards, they are exactly the same. BUT, cows also give leather and milk.
Only enchant diamond tools (if you have some!)
Enchanting doesn't really change depending on the material out of which your tools are made (except for gold, which allows Sharpness V and Efficiency V). That being said, don't waste your precious experience on tools that will break in a matter of minutes.
Everything burns!
I see a lot of people who desperately need to use their furnace, but who don't have coal (or charcoal). Well, you can burn other stuff than just coal! Actually, you can use planks, saplings, sticks... heck, you can even burn crafting tables! It's not very useful if you have better sources of fuel, but it's still helpful if you're just starting out, and it's a good way to get rid of junk.
Here's a list of all the stuff you can use as fuel:
http://www.minecraftwiki.net/wiki/Furnace#Fuel_efficiency
Make iron tools
This is another thing I see often with new players, they stockpile their iron, and use stone tools to mine. Well, let me tell you this: iron tools are quicker and last longer to the extent that, whilst mining, you'll usually end up with more iron in the same amount of time using iron tools as you would with stone tools, even factoring in the cost of the tools themselves!
Bone meal on the ground = flowers!
This isn't really useful unless you intend on building a house out of red and yellow wool, but it's still fun to know. If you right-click a block of grass with some bone meal, the area around it will blossom with flowers and tall grass.
Sugar canes for air
You've found a nice patch of clay at the bottom of the ocean and you want to dig it up? Instead of drowning, plant a two-block tall sugar cane near said clay, and that creates an air patch that you can use whenever you're in need of some oxygen!
Mine near bedrock
You'll never find diamond (or emerald) if you mine near sea level. Instead, you should dig in the first 15 levels of the map, since that's the only levels at which diamonds spawn. To know at what level you are, press F3 and look at the Y coordinate.