Common errors in English:

All ready       
All ready (two words) is used in such sentences as “They are all ready to go”, meaning of all of them are ready.
Already
Already is an adverb meaning previously: “We ran to catch the train, but it had already left”.
All together
All together (two words) is used in such sentences as “They were all together in the same room”, meaning all of them were together.
Altogether
Altogether is an adverb meaning completely: “ You are altogether wrong in your assumption.”
Allusion
Allusion means reference: “He made an allusion to last week’s meeting.”
Illusion
Illusion is an unreality: “that a pair of railroad tracks seems to meet in the distance is an optical illusion.”
Amount
Amount refers to bulk or quantity: amount of sugar, grain, flour, money.
Number
Number refers to objects which are thought of as individual units: number of oranges, children, and diamonds. Notice that most words following amount are singular (coal, butter, water) and that most words following number are plural (apples, bottles, glasses).
Any one
Any one means any single person or thing of a group: “any one of the students in the class was capable of passing the course.”
Anyone
Anyone is an indefinite pronoun meaning anybody: “anyone can tell that you are not so stupid as you pretend”.

 
Bring
 
Brings refers to action toward the writer or speaker: “Bring the book to me.”
Take
Take refers to action away from the writer or speaker: “Take this bottle back to the store.”
Fetch
Fetch means to go and get something and bring it back. “ If you throw the stick into the lake, the dog will fetch it.” However, get is usually substituted for fetch.
Carry
Carry means to convey from one place to another regardless of direction: “ We need a suitcase to carry all our clothes.”
As like
When used as a preposition, like should never introduce a clause (not like I was saying). When introducing a clause, as is used (as I was saying)
As if
If is implied for some of the words of the clause: “He did it as well as I did.”  “They acted as if they were guilty.”
Can
Can implies ability: “Can you (are you able to) lift that heavy box?
May
May denotes permission: “may I (have I permission to) swim in your pool?”
Compare to
Compare to is used to indicate a definite resemblance: “He compared the railroad to a highway.”
Compare with
Compare with is used to indicate an examination of similarities and dissimilarities: “He compared the middle ages with modern times.”