Mistakes

I think that I and my classmates make a lot of basic mistakes.
Sometimes are mitakes that results even funny.
First what happened often is that we are writting in past, and then we write in present, we should write and follow the past tense or the present.
Other mistake is when we don't change the verb when we talk in 3th person.
There are things that we know by heart, but for some reason we keep doing it.
Other mistake, is that sometimes we don't know too much concepts, and we don't know how to explain what we want to say, so we write confusedly, and the paper, the post, etc, is not so clared.
The other common mistake is that sometimes we confused the past participle, or the past simple, or the present continous, when we want to talk in these times, we do not know how to expressed
These in my personal opinion, that are some common mistakes that we make.