Since I don't have much time at the moment, I've decided to tell you about a few helpful things in Minecraft. Some of them are legal and some are "illegal". I'll explain it later. As an experienced player you probably know all of them but I want to help fresh players.
I didn't do anything worth to tell today apart from finding few diamonds. I haven't met volves yet :(.
The diamonds I've found
First trick. Press F3 to turn on some kind of debug mode. Here you can see your FPS (frames per second), coordinates, memory usage etc. but it's a wallhack too. If there's a monster behind a wall, you will see a number above its head. You can use it to find dungeons and with this mode you can go almost everywhere without any equipment (helmet etc.) because monsters won't surprise you. For me it isn't a trick but a cheat. Wallhack makes game very easy to play.
If you play on peaceful, it won't help you.
Always carry a bucket with water and a bucket with lava with you. Water can help you go through some lava caves and lava can help you kill monsters but you won't get loot from them (items burn in it).
Maybe you can't clearly see but I've just spillt water on lava, so it is a safe cave now.
NEVER dig directly under you! If I had stood a block further and dug under me, I'd have fallen into lava. Always dig the block near you, then stand on it and dig the block you were standing a moment before etc.
Always carry cobblestone/dirt/some other easy destructible block, so you can jump out of a hole or block lava/water current.
You jump and then you place a block under you.
You did it!
Here I wanted to show you how to find mob spawners behind walls but couldn't take a screenshot when I pressed "F" so I'll show how to see it for yourself.
Place a torch in a tunnel.
Then wall that torch up, don't turn anywhere and press "F". You should see a fire through the wall. You will see a fire too if there's a mob spawner behind a wall. It is also helpful if you want to see have you been in some place before but you don't want to mine through the wall. You will see your torches. Remember that you can't see through as many blocks as you want.