What is most common bad grammar?

Answer 1

using two past tenses in a sentence is what i have noticed in most of the conversations as bad grammar....for e.g i didn't knew about that...
Bad Grammar is rampant even among well read and articulate people. We English speakers are famous for it. Some of the most popular examples of current bad grammar are:

Mistaken Pronouns, for example "between you and I (instead of me)," "If you have any questions see Mr Jones or myself(instead of me) and "There is is something for we (instead of us) Americans to do."
Lack of Agreement in Number, for example "What we need are ( instead of is) more pots and pans." In that sentence the singular "what" is the subject, not the plural "pots and pans. " Also "Three people fell to their deaths." No, people fall to their death.
The Mushy Protasis in Conditions for example "If I would have ( instead of had) known you were coming I would have baked a cake," and the Sportcasterese "If he catches (instead of had caught) this the game is ( instead of would be) over."

Excessive Use of Of, for example I didn't know it was that long of a walk.

In writing, a big one is Unsure Possessives, for example We met in Charles' (instead of Charles's) office, or at the Jones' ( instead of the Joneses') picnic.
Oddly, I suppose that the most common bad grammar of all, especially in America, is likely to be the expression "aren't I," an abominable Middle Class genteelism foisted on the language by ignorant snobs who shrank from saying "ain't I." Well, "ain't I" is familiar and colloquial English, normal in the Upper and Lower Classes in England. And "aren't I " is simply wrong, and no English at all. Yet almost everyone uses it regularly.

The word "got" is the most overused grammatical error ever heard. I've got, you've got, we've got, etc., should be Ihave, you have, wehave, etc. Blame it on "You've got mail."