Confused word pairs don't usually come from ignorance — they come from writing fast and trusting your ear, which is exactly where English lets you down. These mix-ups rarely change meaning enough to confuse a reader, but they do quietly signal carelessness. A few reliable tricks fix most of them for good.
The pairs that sound almost identical
Affect is usually the verb (the delay affected our schedule); effect is usually the noun (the delay had an effect on our schedule). A quick test: if you can put "an" or "the" in front of it, you probably want effect.
Its shows possession (the company lost its licence); it's is always a contraction of "it is" or "it has" (it's losing its licence). If you can't expand it to "it is," drop the apostrophe.
Their, there, and they're follow the same logic: their owns something, there points to a place, they're is short for "they are." Read the sentence back and swap in "they are" — if it still makes sense, that's your spelling.
The pairs that mean almost the same thing
Fewer is for things you count (fewer emails); less is for things you measure (less traffic). Compliment is praise; complement is something that completes another thing — a complement completes, and both words share that middle e.
Build your own list
Everyone has a personal set of two or three words that trip them up, often the same ones every time. Keep a short note of yours and check it before you hit publish — it's faster than trying to memorise every confusable pair in the language, and it targets the mistakes you actually make.
