1. Using the same rag around the whole house. It just transfers dirt from the first surface and spreads it to the next one. Instead, you should use disposable wipes or have a rag for each room that gets washed after using it.
2. Spraying cleaner directly on a surface. Spraying cleaner directly onto counter tops, mirrors, or glass can cause a buildup of the cleaning solution, and THAT can make dirt harder to remove and cause streaking. Instead, spray your rag or paper towel, THEN wipe.
3. Using a feather duster. Feather dusters are notorious for spreading dust around rather than removing it. A microfiber cleaning cloth is a better option.
4. Not cleaning your vacuum. If your vacuum filter hasn't been changed or cleaned in a while, the vacuum can't pick up as much dirt and dust as it should. And the dirty vent could even blow back dust into the air and carpet.
5. Putting the toilet brush back into its holder immediately. Moisture and germs from the toilet can get trapped in the container and the brush, and those germs get rubbed back into your toilet the next time you use it. So let the toilet brush dry completely before you put it back in its holder.
6. Cleaning from the ground up. If you sweep, mop, or vacuum before cleaning everything else, dust and crumbs will just fall and get the floor dirty again. So always clean a room from the top down and hit the floors last.