1. its and it's
Honestly, if you're still messing this one up you shouldn't be writing for advertising.
TIP: generally in English, an 's adds is to the word your modifying. "It's cold. The heat's gone. Let's get out of here." this example shows usage, respectively, of the 's abbreviating is, has and us.
It is an easy one, if it has an apostrophe it stands for it is, if it doesn't it shows possession. "It's over there" or "Its construction has been ongoing for a month."
2. their, there, and they're
Their refers to someone's possession.
There refers to a place.
They're is short for they are.
EXAMPLES:
Their bed wasn't made all day
The bed is always over there, by the door.
They're always eating the right types of food.
3. your and you're
My most hated, and easiest to spot error.
Your = possessive form of you. EXAMPLES: Your nose. Your bed. Your window.
You're = abbreviated you are. EXAMPLES: You're wet. You're hot. You're smart.
PLEASE GET IT RIGHT!
4. Dangling participle
You may not recognize the name of the error, but here are some examples. I'm sure it'll all come back.
Walking to the store, a tree almost fell on me.
what it means: a tree was walking to the store.
Running from the police, my shirt and pants were ripped off on a fence post.
what it means: your shirt and pants were running from the police.
Both of these can be easily fixed by adding "While I was..." in front of the sentence. The dangling participle can always be fixed easily, but is often overlooked.
5. e.g. and i.e.
OK, most people who think these two are interchangeable are WRONG. If you use them in the wrong way, you're bound to look stupid.
e.g. = exempli gratia, which means "for example".
i.e. = id est, which means "that is".
So, you want to use e.g. when you want to give an example, or give several examples. You want to use i.e. when you want to restate what you just said in other words, or to clarify what you just said.
EXAMPLES:
The new super hero showed fantastic telekinetic abilities (i.e. the ability to move things with your mind).
The new super hero had many different abilities, e.g., shape-shifting, flying, and super speed.
Don't be considered uneducated, get the usage right!
6. loose and lose
It's an error that is so frequent I had to add it to the list. This is simply a spelling error.
(Lose means something is gone that was once there. Loose means something is less tight than it once was.)
EASY WAY TO STOP MAKING THE ERROR:
When you want to use lose. Lose one of the o's.
When you want to use loose. Loosen the word by adding an o.
It's dumb, and kind of inaccurate, but it works well.
7. that and which
Ok, the most simple explanation is:
THAT is used for identification
WHICH is used for description
EXAMPLES:
This is the color that you asked for, right? (Identifies the color)
This is the color which will be used on your car, right? (Describes the color)
Most editors will catch this error, but do yourself a favor and try not to make it in the first place.
8. affect and effect
This is here because it's common, but easy to avoid.
AFFECT (to affect) = influences something. Magnets affect television reception.
EFFECT (an effect) = a result of something. Magnets cause a distortion effect on television screens.
9. misplaced or dangling modifiers
Generally, this just means there is a word, or group of words, that don't have a clear referral within the sentence.
EXAMPLE:
Using a cup, the water was bailed from the boat.
(The water didn't use the cup, and the cup wasn't bailed from the boat.)
Usually, this would be fixed by saying: He bailed the water from the boat using a cup.
10. comma splice
Simple. This happens when you have 2 main clauses connected by a comma.
EXAMPLE:
When you add boiling water to Jell-o, you get a liquid, solid Jell-o is only achieved after it sets in a cool place.
3 easy fixes:
Replace with a period:
When you add boiling water to Jell-o, you get a liquid. Solid Jell-o is only achieved after it sets in a cool place.
Add a conjunction:
When you add boiling water to Jell-o, you get a liquid, but solid Jell-o is only achieved after it sets in a cool place.
Replace with a semicolon:
When you add boiling water to Jell-o, you get a liquid; solid Jell-o is only achieved after it sets in a cool place.
Avoid these main grammar errors and avoid looking stupid!