The subject of a sentence and the verb of a sentence must agree with one another: "A person is smart, people are dumb, stupid panicky animals." This can get a little complicated, though, when there are prepositional phrases between the subject and the verb: "A bunch of people spells trouble."
The subject of a sentence is never found in a prepositional phrase; if a noun appears after a word like of, the one thing you can be sure of is that it's not the subject. Collective nouns such as "group" and "bunch" and "pile" are singular, not plural; the plural versions are groups, bunches, and piles. So you would say "A group is going" or "Two groups are going."
When a prepositional phrase follows the subject, the verb must still agree with the subject, not the prepositional phrase. So you would say "A group of people is going to the movies," not "a group of people are going to the movies"--the phrase 'of people' is a prepositional phrase, and is not the subject of the sentence. (You would correctly say "two groups of people are going to the movies;" the plural of "group" is "groups.")
On a similar note, the proper first-person pronouns used as objects of prepositions and active verbs are "me" and "us," not "I" and "we." For example, "can you give Tommy and me a ride to the store" is correct; "can you give Tommy and I a ride to the store" is not. When you remove Tommy from the equation, this becomes easier to see; you would say "Can you give me a ride" but never "Can you give I a ride" or "Can you give myself a ride."
"Orientate," "preventative," ...
These are errors which occur when someone attempts to add prefixes or suffixes to a word inappropriately, resulting in an awkward or incorrect construction.
It's "administer," not "administrate."
When you supervise something, or when you apply something or dispense something, you are "administering" that thing, not "administrating" that thing. You would correctly say "Bob will administer bandages and aspirin," not "Bob will administrate bandages and aspirin." (Some references are beginning to recognize "administrate" as an acceptable, but less preferred, alternative.)
It's "preventive," not "preventative."
Something which is designed to prevent something else from happening is a preventive measure, as in "aspirin can act as preventive medicine for heart attacks."
"Orient" is generally more acceptable than "orientate."
When you have your bearings, you are properly "oriented." The process of becoming oriented is called "orientation," but if you are giving something or someone its bearings, you are orienting it, not orientating it.
The word "orient" originally meant "to face east" (that is, quite literally, to face toward the Orient when one is in Western Europe). "Orientate" originated in Great Britain as a word meaning "to line up properly" even when "properly" didn't mean "facing east," but fell into disuse as "orient" came to be more general in its applications. Today, "orientate" is considered incorrect in American English, though I'm told it's still considered an accepted variant on "orient" in British English.
It's "regardless," not "irregardless."
This one is a bit confusing, because "irrespective" is the correct form of "not respective" (as in "all employees receive the same vacation benefits irrespective of their seniority"), but the correct form of "without regard to" is "regardless," not "irregardless."
It's "empathic," not "empathetic."
"Empathy" is the ability to understand and identify with another person's feelings. A person who has a high degree of empathy is a person who is good at understanding the feelings of other people, and is said to be "empathic."
It's "supposedly," not "supposably."
The word "supposedly" means "purportedly," as in something which is believed to be true. "The defendant supposedly hit little old ladies on the head and took their Bingo money," for example. The word "supposably" is rarely used, and means "able to be supposed," which is something else entirely.
It's "non-stop" or "nonstop," not "none-stop" or "nonestop."
"Non-stop" means "without stopping." The prefix "non" means "without" or "not," as in "nonsense" (without sense), "non-toxic" (not poisonous), and "nonexplosive" (not explosive). Under no circumstances would you say "none-stop," "nonesense," "none-toxic," or "noneexplosive."
"I feel badly" and "I feel bad"
When you feel a negative emotion, you do not feel badly; you feel bad. "Badly" is an adverb, which means it modifies a verb; if you "feel badly," that means your sense of touch has been impaired and you are bad at feeling things.