1. Lets and Let's
"Lets" is the third-person form of the verb "let." E.g., He lets me eat cake all the time.
"Let's" is the contracted form of "Let us." E.g., Let's go dancing tonight!
2. Awhile and a while
"Awhile" is an adverb meaning "for a short time" and is used to modify verbs. E.g., She played the piano awhile.
"A while" is a noun phrase consisting of the article "a" and the noun "while" and means "a period or interval of time." It is often used with a preposition. E.g., I'll be coming in a while.
3. Affect and effect
"Affect" is most commonly used as a verb meaning "to influence or impact something." E.g., Her depression started to affect the family life.
"Effect" is most commonly used as a noun meaning "the result of something." E.g., The beneficial effects of exercise are evident.
In rarer cases "effect" is also used as a verb meaning "to cause something to happen." E.g., The prime minister hopes to effect reconciliation between the opposing parties.
4. Each others and each other's
"Each others" is the plural form of each other, but it's not appropriate to use it. You most likely meant "each other," e.g., Pete and Mary love each other very much.
"Each other's" is the possessive form that indicates belonging to someone or something. E.g., We tried on each other's dresses.
5. Years experience and years' experience
"Years experience" is always incorrect.
"Years' experience" is the correct form. It's the possessive form meaning "years of experience" or "experience belonging to years." E.g., He has five years' experience as an airline pilot.
6. A and an
"A" is the article used in front of a noun that starts with a consonant or a consonant sound. E.g., We saw a fox on our way home last night.
"An" is the article used in front of a noun that starts with a vowel or a vowel sound (sometimes the "h" can be silent). E.g., We saw an owl in our back garden this morning. Or, It was an honor to be at your wedding.
7. Everyday and every day
"Everyday" is an adjective meaning "commonplace, ordinary, or daily." E.g., I don't like these everyday dresses they sell in that shop.
"Every day" is an adjective (every) modifying a noun meaning "each day." E.g., I cycle to school every day.
8. You and your
"You" is the second-person pronoun and can be used as the subject or the object of a sentence. E.g., I can't believe you always win the raffle. Or I saw you at the movies last night.
"Your" is the possessive form of "you" which indicates that something belongs to you. E.g., Can I borrow your car tomorrow to drive to Las Vegas?
9. Advice and advise
"Advice" is a noun meaning "recommendation, guidance." E.g., My father's advice was always very precious to me.
"Advise" is a verb meaning "to recommend, to inform, to warn." E.g., Your father will advise you if you ask him to.
10. Its and it's
"Its" is the possessive form of the pronoun "it" indicating that something belongs to "it." E.g., The dog always loses its toys.
"It's" is the contracted form of "it is" or "it has." E.g., It's raining again.
Article from: https://finance.yahoo.com/news/most-commonly-confused-words-english-153000638.html