The last part of the tip might be for just a niche audience, but with command blocks you could create items with no despawn rate and use it as decoration for environment-unfriendly areas like waterpipes dumping trash and water into a lake.
Reinforcement zombies Don't only have the different spawning condition of being able to spawn in light level 9. They can also spawn on bedrock, and on things that mobs normally can't spawn on, like redstone and pressure plates. If you have a spot that's covered by redstone, a pressure plate, or it's over bedrock, remember that reinforcement zombies can still spawn there unless the light level is at least 10.
If you put glass as the floor of your blaze farm, whenever they shoot their fireballs the glass will not catch on fire, because glass won't ignite. This is very helpful if you keep losing experience/blaze rods from the fires that they create!
This is tip may seem useless, but coming from a particularly lazy person, it's saved me a lot of time. When you're chopping down a tree, break the bottom block last so you can jump on it if theres one or two out of your reach. This saves you the trouble of putting down a new block to jump on, and reduces the amount of floating trees that clutter your world.