These are three of the easiest mistakes to prevent in copy. So why do people make them?
Listen, I don't like playing the role of a hectoring grouch. I know I've written about the first of these mistakes a couple of times before. I've probably hinted at the other two as well. Nothing would please me more than writing about puppies, or kittens, or flying kites on a bright summer's day.
But the mistakes continue. I must confront them. I step into my hectoring grouch costume, and the heroic struggle continues.
1.) It's/Its.
One of the most common slips. You use the apostrophe when you're contracting "it" and "is." When you make "it" possessive, you do not use an apostrophe.
2.) Affect/Effect
The first is a verb. The second is a noun (it can sometimes be a verb, but that needn't concern us here). They can be easily confused, so take a moment to remember.
"It affected me deeply."
"It must have had a great effect, then."
3.) Comma Rule
Many exist. I gripe about one. If you have two complete thoughts joined by linking word such as "and" or "but," put a comma before the linking word.
Thus:
"She enjoyed roller-skating, and she was good at it."
If the second part of the sentence doesn't have a subject, the thought is no longer complete. You therefore do not use the comma.
"She enjoyed roller-skating and was good at it."