I mentioned these in the article about avoiding adverbs. The point, though, is important to mention on its own.
I see the word "slightly" several times a chapter in inexperienced writer's fiction.
It was raining slightly.
Why just slightly? Was the author worried about his character getting too wet? What's wrong with the character having to cover his head with his brief case and dash through the puddles? Unless you have a specific reason not to inconvenience your character, putting stress on the character is much better. Now he's worried that someone will notice the wet pant legs, or he's chiding himself for not bringing an umbrella. Those are examples of micro-tension, which elevates your writing out of the trivial.
His head ached slightly.
Well, isn't that sad. Why not show him trying his best to hide his pounding headache? Again, that adds drama, increases the pressure on your character, and ups the micro-tension in the scene.
Often, the minimizing word just isn't needed.
She gave a slight hesitation.
Better: She hesitated.
Other minimizing words include little, a little bit, tiny, a tad, and brief.
He felt a little nauseous.
Why not make him sick to his stomach but doing his best to cope?