Let's face it, English can be confusing. A lot of words are similar but with different meanings. It is almost impossible to avoid making mistakes in English, but you might be able to avoid making these ones.
Here are some common mistakes and answers: http://www.learnenglish.de/mistakes/CommonMistakes.htm
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accept vs except | advice vs advise
affect vs effect | a lot/alot/allot
all ready vs already | all right vs alright | alone vs lonely
altogether vs all together | ambivalent vs indifferent
any vs some
any one vs anyone | apart vs a part
been vs gone | beside vs besides
bored vs boring | borrow vs lend
bought vs brought | by vs until
check vs control | come over vs overcome
complement vs compliment
concentrate vs concentrated | council vs counsel
councillor vs counsellor
data vs datum | decent vs descent
defrost vs melt
do or make | discreet vs discrete
don't have to vs mustn't | downside vs underside
driving test vs test drive
effect vs affect | e.g. or i.e. | either or vs neither nor
either vs as well / too
enquire vs inquire | enquiry vs inquiry
every day vs everyday | excited vs exciting
expand vs expend | experience vs experience(s)
fewer vs less | for vs since (time) | good vs well | gone vs been
hard vs hardly | hear vs listen | heroin vs heroine | he's vs his
holiday vs the weekend | homework vs housework
"How do you do?" vs "How are you?"
I vs me | improve vs improvise
inquire vs enquire | inquiry vs enquiry
interested vs interesting
lay vs lie | lay down vs lie down | less vs fewer
look after vs look for | look at vs watch
look forward(s) | look forward to
look over vs overlook | loose vs lose
me vs I | me vs my | moan vs mourn
most vs the most | most vs mostly
nor vs or
overtake vs takeover / take over
personal vs personnel | practice vs practise
precede vs proceed | principal vs principle
quiet vs quite
raise/rise | regard vs regardless vs regards
remember vs remind | replay vs reply
said vs told | see vs watch | shortage vs shortness
so vs such | some vs any | stationary vs stationery
take care vs take care of | that/which/who | to/too/two| there/their/they're
trainer vs trainee | travel/trip/voyage/journey
used to vs used to do
wander vs wonder | what vs which | who vs whom
wrong vs wrongly
