I read a few of our newspapers and blogs and cringe anytime I see these errors. They are very common errors and also very easy to fix. You just have to know the grammatical rule that applies and you'll find yourself getting it right each time.
It's worth it to speak correctly because how we speak dictates how we are perceived by others.
1. when to use do/does
Simply put "They does not" is incorrect. The correct grammar is They do not. follow these simple rules
He does not see it
She does not see it
They do not see it
We do not see it
I do not not see it
You do not see it
2. When to use worse or worst.
Use worse when comparing two things, people, time etc. for example: This government is worse than the last one
Use worst when comparing 3 or more things, people, time, etc. For example: this government is the worst one ever
Don't say Uche is a worst actress than Ngozi. You are comparing only 2 people so use worse.
3. When to use It's or Its.
Simple rule for this is use it's only if it would be proper to say "it is." It's is the short form of "It is" so if you can't say it is then you shouldn't be saying It's.
for example it is a long way from here or it's a long way from here.
let us find its juncture. you can't use it's there because you can't say let us find it is juncture
4. When to use their or there:
Their refers to a group. Their room is next to my room.
There refers to a place. Let us go there
5. When to use your or you're. This is a somewhat new mistake people are making. But it's very easy to correct. You're is the short form of you are. Only use you're if you could also say "you are." For example you're making me sick or you are making me sick.