In the Normal world, most of the things I encounter I defeat with kiting - draw the Creeper/Zombie/Spider to me, hit them whilst backing up, and if it's a Creeper, back up further if it starts to sizzle. Doesn't work with Skeletons, so I ignore them until I can craft a bow and arrow, then just shoot at them whilst dodging their arrows. Also, I typically fight only one monster at a time, put torches everywhere to avoid them spawning in the first place, and try and get the high ground. If I come across a dungeon I'll tunnel above it, then attack them from on high, unless it's a Skeleton Dungeon, in which case I'll just tunnel above it and drop some TNT on their heads.
I tend to use sound a lot to tell where enemies are coming from. Listening for footsteps has saved my life against Creepers - they make no idle sound, but they make footsteps. At this point though, I'm almost always wearing a full set of Iron Armour so I'm not that cautious any more.
As for the Nether, I bring lots of Cobblestone, and use it to build walls I can hide behind when Ghasts start spitting fireballs at me, and I'll fire on them with a bow if they get very close as they're easy to hit. And I just leave the Zombie Pigs alone, no need to fight those guys, I'll just bring food with me.
I tend to use sound a lot to tell where enemies are coming from. Listening for footsteps has saved my life against Creepers - they make no idle sound, but they make footsteps. At this point though, I'm almost always wearing a full set of Iron Armour so I'm not that cautious any more.
As for the Nether, I bring lots of Cobblestone, and use it to build walls I can hide behind when Ghasts start spitting fireballs at me, and I'll fire on them with a bow if they get very close as they're easy to hit. And I just leave the Zombie Pigs alone, no need to fight those guys, I'll just bring food with me.