I was playing minecraft one day, and I was wondering if there was any good method to protecting my house automatically (While not using Golems!) from angry mobs. Is there any way to install a system that protects my house from evil baddies?
This question is fairly broad. Home security is going to need several different pieces to deal with the different behaviors of the different mobs. Additionally, if you care about the defenses "fitting in" to the overall look of your home/biome, then some solutions may not be acceptable. Furthermore, some biomes can have more options, for example deserts can take advantage of the sand and it's obeying gravity. Despite those, here are some suggestions.
The best way to prevent spawning monsters is to light the place up.
the light level of the spawning block must be 7 or darker
Another good way to prevent monsters from coming close is to put a fence around your land. Spiders can climb fences and Endermen have a chance of teleporting, but other mobs will be stuck. However, skeletons can shoot over the fence.
Yet another option would be to build upward. Make your main level a couple blocks above the ground and bring the outer walls down. This way mobs are stuck below your door without falling into anything.
Spiders can climb walls, so we need to figure out how to stop that. Spiders cannot climb over signs. You could also include a lip or ladder at the top of the wall. Since spiders are 2 wide and 2 long, planting cactus around your house will damage spiders as well, though I believe you need to add extra to the top if you want to fully kill it before it crosses the top.
Skeletons shoot arrows. Sugar cane used to be able to block projectiles, but that has been patched. You can use glass in your windows to avoid taking damage inside your house. To avoid them reaching your house, you can use a ditch or moat similar to zombie/creeper defenses.
Endermen hate water (and lava), though they are normally neutral. If you can cover spaces around your house with water, that can help prevent them from teleporting near. They also require and area 3 blocks tall, so having a roof can prevent their teleporting/spawning.
Witches are kind of like smarter zombies. When damaged, they try to heal. When under water, they drink potion of water-breathing. When on fire, they drink potion of fire resistance. They also use splash potions as weapons, making them ranged enemies. Best option here is probably to just use a ditch and get them stuck.
Zombies come in many shapes and sizes. Some can even fit through a 1 block hole. To defend against them, you can have a moat of that directs them away from your door, have a moat of lava that kills them, or have a pit that traps them.
Slime is unlikely to be bothering you, but if you have some problems with them they can mostly be dealt with similar to zombies.
Lava around your house works for zombies a lot of the time.