1. What is a run-on?
A run-on is a sentence that contains two independent clauses, in other words, a sentence that is really two sentences in one.

2. How to fix a run-on sentence:
Break it apart into two sentences
Ex. Run-on: The weather was bad, the meeting was poorly attended.
Correct: The weather was bad. The meeting was poorly attended.

3. How to fix a run-on sentence:
2. Add a semi-colon if the two ideas are closely related. Even better, add a semicolon and a conjunctive adverb:
Ex. Run-on: The weather was bad, the meeting was poorly attended.
Correct: The weather was bad; the meeting was poorly attended.
OR: The weather was bad; therefore, the meeting was poorly attended.

4. How to fix a run-on sentence:
3. Add a comma and a conjunction
Ex. Run-on: The weather was bad, the meeting was poorly attended.
Correct: The weather was bad, so the meeting was poorly attended.
OR: The meeting was poorly attended because the weather was bad.
Note: when the clauses are short and do not already contain commas, you can get away with just a conjunction

5. How to fix a run-on sentence:
4. Re-word it to combine the clauses or make one clause dependent Ex. Run-on: The weather was bad, the meeting was poorly attended. Correct: Because the weather was bad, the meeting was poorly attended. Or: The bad weather probably caused the meeting’s poor attendance.

6. What is parallelism?
Parallel phrases or clauses are about the same length and follow the same grammatical structure (i.e. same parts of speech, verb tense, etc.)

7. How to fix faulty parallelism
Convert all the verbs to the same tense:
Instead of something like this: During class, Samuel spent his time flirting with Brittney, he ate candy, and doodling on the assignment sheet.
Change that past tense verb to a past participle like in the other phrases: During class, Samuel spent his time flirting with Brittney, eating candy, and doodling on the assignment sheet.
Notice we also removed he so the word order is the same throughout too.

8. How to fix faulty parallelism
Make sure the same parts of speech are present and in the same order:
Instead of something like this: Alex looked everywhere for his math book—viewing under the bed, searching on his desk, and inside the refrigerator.
Make each phrase go preposition – modifier - noun: Alex looked everywhere for his math book—under the bed, on his desk, and inside the refrigerator.
Notice this is simpler and sounds less awkward too!

9. Let’s try that one more time:
Instead of something like this: Eileen bought new shoes for the party, a gold charm for her mother, and to treat her best friend Maria to lunch.
Get rid of that icky infinitive! Eileen purchased new shoes for the party, a gold charm for her mother, and lunch for Maria.
Instead of something like this: Dogs that bark, kittens that meow, and parakeets squawking greet the pet shop visitors.
Make those phrases parallel!: Barking dogs, meowing kittens, and squawking parakeets greet the pet shop visitors.
Notice you can take out or rearrange the parallel phrases in either example and the sentence still reads correctly.