Traps/ Water n Lava control

Any suggestions on how the heck I can control water flow or lava for traps n such?

So far I have been using a sand block to hold back lava in a wall as a trap to hit when I am being chased by spiders n such.

I know that water cant pass through doors... Any good ideas?

You could dig a hole and fill it with lava and then close to that make a stone box and fill it with water but in the side of the wall that faces the lava pitt, place a TNT and connect it to some redstone and a preassure pad.
When you're running from an enemy you hit the switch and leave yourself enough time to run past the pit and water box, leading the enemy between them so the TNT blows the wall and the water sweeps the enemy into the pitt. Never really tried traps makin yet myself but i think that might work.

Make 2 Paths, one Filled with water and one to wherever you're going block the water path with an iron door and put a pressure pad linked to the door with redstone on the clean path, so when you run over it, water will be released.

good idea Jasix.

eatmoretoast47 can water pass through iron doors now? I'm at work so i cant rly check at the moment...

Well, I figure it'll pass through an open door, unless the FIZIKS level is really high