Dangling Modifiers

A dangling modifier is a word or a phrase that modifies a word that is not clearly stated in a sentence. 

For example:

While waiting for the doctor to examine her, she was bored.

The sentence has no error. You have to check that the subject after the comma is the doer of the verb.

She was bored while waiting for the doctor.

Having finished the homework, the lights were on. 

The sentence is incorrect because "lights" can't finish homework!

Double Negatives

A Double negative occurs when a sentence has 2 negative words. 

Here's a list of some negative words:

Scarcely- barely- rarely- hardly- seldom- never- ever- no- not- nobody- nothing- none- only.

Faulty Comparison

The secret to faulty comparison is to make sure that you are comparing two things equally. 

For example:

The yellow ball can jump higher than all of the balls.
The sentence may seem correct but it's not. There is a comparison between a ball's ability of bouncing and balls, which doesn't make sense.
The correct sentence would look like this: The yellow ball can jump higher than all of the balls can.

Parallelism

Parallelism is a series of related words or a list of items. Nouns are listed with nouns, words ending with -ing are listed with words ending with -ing, and so on. The secret to parallelism is to make sure everything is the same.

For example:

My plans for tonight are shopping, seeing friends, and watching movies. 

When I get home, I am going to eat dinner, do my homework, and go to bed.

 The previous two examples show parallel construction as in the 1st example, all the words ended with -ing, and in the 2nd example, all the verbs were in the infinitive form.

I am going to see my friends, take a test, and helping my mum with chores this week.

This sentence is not parallel because the 1st two items on the list are verbs in the infinitive form, and the 3rd item is in the -ing form.

Subject- Verb Agreement

Subject- verb agreement: When a subject doesn't agree with its verb in number.

For example: 

Tonight, Mike and I are hanging out.

The underlined words are the subject and the verb. There is no error in this sentence because 'Mike and I' are plural, and 'are' is plural, thus agreeing in number.

The child sings beautifully. 

The underlined words are the subject and the verb. There is no error in this sentence because 'child' is singular, and 'sings' is singular, too.

School are boring.
The error in this sentence is obvious. School is singular, and are is plural. 

The problem is that there are words that are usually thought to be singular or plural, but they're not. Here's a list of some of these words:

Singular words:

The- Everyone- Everybody- Everything- Some- Nobody- No one- Anyone- Someone- All- Each- Neither (without nor)- Either (without or).

Plural words:

Either/ or- Neither/ nor- And- A.

When you see any of these conjunctions in a sentence with more than one subject, the 1st subject determines the verb:
As well as- together with- along with- in addition to.

When you see any of these conjunctions in a sentence with more than one subject, the subject closest to the verb determines the verb:
Neither/ nor- either/or- not only/ but also- not only, but/ as well.