SOS

This stands for Simultaneous Oral Spelling: it is useful way of learning spellings, particularly for anyone with mild dyslexia.
It means that you write down the spelling, saying each letter as you write it.
It is known as a multi-sensory method as you are using your visual, auditory and kinaesthetic senses to implant the word.

SUBJECTIVE and OBJECTIVE

Subjective means that the view taken of something is subject to the emotions and opinions of the viewer.
Objective means that the object in question is being looked at without feeling. (Some would say this is impossible.)
A writer might look at a flower and feel its beauty subjectively, pondering on the fact that it will soon die, whereas a gardener might think objectively about the best conditions for its growth.

CONTINUOUS and CONTINUAL

Continuous means without a break: The noise from his lawn-mower was continuous.
Continual means repeated frequently but with pauses between.  He received continual
bad reports.
A good way to remember is that continuous noises often make you angry and want to hiss:
continoussssss.

SILENT 'E' RULE

This is sometimes called magic or lazy e.
Drop the final e before a vowel suffix: like liking.
BUT keep it before a consonant suffix: like likely

ing is a vowel suffix because it begins with a vowel and ly is a consonant suffix because it starts with a consonant.

The reason is that the vowel in the new ending will keep the first vowel long just as the e did. Drop the e when you do not need it.  N.B. manageable where the e keeps the g soft.
Exceptions: vicious, artificial, racial etc.  The i here does not lengthen the first vowel because it forms a sh sound which alerts you to the exception.

EMBLEM

An emblem is similar to a symbol except that it is more limited in its meaning and often has a direct reference to just one object. Whereas the conch in Lord of the Flies has many significances: civilisation, order, comradeship, leadership etc., the daffodil, as emblem of Wales, means just that country. It also carries its reference with it: a daffodil indicates Wales to anyone, whereas a conch means civilsation only within the novel. A literary example would be the violet in the seventeenth century which was widely accepted as an emblem of faithful love and truth.

TO, TWO and TWO

To is the simplest: it is a preposition and often forms a phrase with a noun: She went to the shops.
Two is the spelling for the number: two eggs.  A good way to remember is that there is a w in it just as there is in twice.
Too is the spelling when something is too much.  Think of yourself saying it in a dramatic way: "It is all toooooo much" and then you will remember that there is more than one o.

Symbol

A symbol is an object which develops deeper meanings, sometimes during the course of a literary work. In "Lord of the Flies" the conch becomes a symbol of civilisation and order. Yet it is a "real" shell present in the narrative also.
In simile or metaphor the compared object is not real or present. If we speak of her "shell-like ears" there is no shell present in the discourse. Similarly in: "He retreated into his shell", there is no real shell.

Hopefully

There is only one safe rule about using the word hopefully and that is: avoid it.
Hopefully is an adverb and should describe a verb: in the sentence, "Hopefully the parcel will arrive tomorrow", the parcel itself is almost hoping it will arrive.
To avoid it, say, "I hope the parcel will arrive tomorrow."

YOU'RE and YOUR

You're means You are with the apostrophe signalling the missing letter a.
Your means belonging to you.

A good way to remember is that your includes the letters that spell our. Your.

WHETHER ... OR

Whether should always be followed by or. 
I will go whether it is wet or fine.

If there is no obvious alternative, simply add or not.
I do not know whether to go or not. 

METAPHOR

A metaphor compares two things which are not usually considered similar and finds something in common between them.  It does not use the words like or as.
Example: After the storm we were cocooned in our caravan.
The caravan is not a cocoon but it is warm, protective and cosy like a cocoon.
Some metaphors are so overused that they become dead metaphors: She is a bright girl. The girl's intelligence is compared to a light but it is not a fresh way of saying this.

SIMILE

A simile is a comparison between two differing objects which requires a leap of the imagination to see the similarity.  The comparison is made obvious and explicit usually by  the use of the words: as or like:
"Her eyes were as blue as a cornflower." Eyes and cornflowers are very different things, apart from their being blue.  If you were to say: "Her eyes are blue like her sister's," you are not using simile as the two sets of eyes are similar and no imagination is needed to see what they have in common.
The word simile is often wrongly spelled: think of it as having the same number of syllables as metaphor and do not omit the middle i.  Or you can think of it as being like the word similar and you will not forget the spelling.

LOSE and LOOSE

Lose is a verb: "I am afraid I may lose my new mobile."
Loose is an adjective: "My shoelace has come loose."

A good way to remember is to think of yourself shouting out, exaggerating the vowels: "My shooooooelace has come loooooose!"  This tells you that the word has a long sound but, of course, only two letters o.

LY as a SUFFIX

A suffix is a small group of letters (here just two) which you tack on to the end of a word to change its usage or meaning.
Ly changes an adjective (which describes a noun) into an adverb (which describes a verb.)
You simply add it on without altering the original word - do not take any letters off and do not attach any new ones. Therefore sincere becomes sincerely, truthful becomes truthfully and so on.
The main exception is true which becomes truly.

With many of these rules there are other minor exceptions but, if you learn the main ones, you will have improved your performance in an examination or in a letter.

BLANK VERSE

Blank verse is not the same as free verse which has no set rules.
Blank verse is unrhymed iambic pentameters.
Unrhymed means that there is no rhyme at the end of the lines, although Shakespeare frequently adds rhyme at the end of a scene to show that it is the end.
Iambic means that each foot (little bit of the rhythm) reads like the word again.with a weak stress followed by a strong stress.
Pentameter means that there are five of these feet in each line
Therefore a line of blank verse reads as though you are saying the word again five times:
Again, again, again, again, again.

YOUR and YOU'RE

You're means you are.  The apostrophe shows a missing letter.
YOUR means belonging to you.

Think of your as including the word our.

NEITHER .. NOR

Neither ...nor takes a singular verb.  Neither my brother nor my sister likes tennis.

If you are not sure what the right verb is, try using just one of the people concerned: my brother likes tennis.  Although this sentence does not mean what you want to say, it does give you the correct form of the verb

PRACTICE and PRACTISE

Practice is a noun. We went to the football practice.
Practise is a verb.  You must practise the piano.

The best way to remember is to think of advice and advise where you can hear the difference.

THEY'RE, THEIR and THERE

They're means they are. The apostrophe here tells you that there is a missing letter.
Their means belonging to them. It does not need an apostrophe because it is a possessive adjective.
There means in the place being pointed out: over there. A good way to remember it is to see the word here in it as those meanings are, in a way, opposites.

IMPLY and INFER

The writer implies.
The reader infers.
Sherlock Holmes infers.

To imply means to hint or suggest.
To infer means to work out or deduce.
Remember it by thinking that there is an r in read and in infer.

IT'S and ITS

It's means it is.  It's raining now. The apostrophe shows a missing letter.
Its means belonging to it. The dog wagged its tail.

You do not need the apostrophe in its tail because its is a possessive adjective and shows possession, that the tail beongs to the dog, without any apostrophe.