I’m not saying to never use these words.  Just make sure that your sentences don’t contain too many of them.

• That — often put in as a filler word. 
• Had — same thing.
• Color words — used lots of times as ways to give something more description.  They often aren’t needed.  If the grass is purple, point it out.  I think I can guess it when the grass is green.
• Hair — a lot of times, I see a character’s hair described every single time that character is in a scene.
• Pleonasms — it almost goes without saying.
• Strife — it’s a decent word that everybody knows, but it leaves a bad taste in my mouth because I never really see it outside of people trying to sound fancy.
• Doom — It used to be used a lot more, making even minimal usage today sound silly.
• Neutron — it’s a normal little particle in an atom’s nucleus, not a catch-all term synonymous with magic.