Without further adieu:
"It works good." "It plays real good." Any usage of the word "good" for "well" creates an immediate impulse for correction. I have actually hear this usage from one of the my child's pre-school teachers. My significant other is being continually subjected to this correction, much to his chagrin. We live in the southwest, we have college degrees, therefore there is no reason to subject your audience to this incorrect term usage. There shouldn't be a reason if one has graduated from junior high, yet it persists.
The action of ending a sentence with a preposition. "Where's it at?" "Where are we going to?"
"Anyways" There is no "s" on the end of "anyway."
"Located" as a redundancy, as in: "Where is it located?" I regularly strike out the word when used similarly by my employees or colleagues. True writing skill is getting the most across with the least amount of words.
Loss of definite articles, such as the British usage "He went to hospital." No, "he went to THE hospital."
Finally, a misspelling that is a clear indication of never having seen the correct spelling of the word. Examples I have seen recently: "Escavate" for excavate (the writer is first generation American of Hispanic origin and so I give him/her great credit for trying) and "spicket" for spigot. Enough said.