Tenses. No, not the plural of tense ??? which is actually an adjective, not a noun. These are those icky-poo things that people make such a bother about. "Always write essays in the present tense!" (which is true); "Use the past perfect tense, not the perfect!" But now, you can be more educated than most of your teachers, with this handy-dandy list and how-to to most the tenses in the English language. Descriptions follow, along with the formation of each tense in bold. (Postscript: articles shall from now on be written about specific subjects, not all helter-skelter and chaotic. Nouns, subject-verb agreement, one a week. Although, chaos is fun!)

The Tenses

Present: This is the most basic tense, and uses the present tense of a verb, and states facts that are occurring now.
Subject + first principal part (present form of verb)
I am a prolific user of the Internet.

Present Progressive: Sometimes not considered a separate tense, it states facts that are occurring right this moment. It usually uses the gerund* form of a verb, plus a helping verb**.
Subject + am/is/are + gerund (verb-ing)
I am currently writing an article for the WhyTimes.

Past/Perfect: Used for events that have already occurred, and only once. Oftentimes, the past tense form of a verb is the infinitive*** plus ???ed, usually.
Subject + past tense form (verb-ed)
I incited action into the hearts of Whyvillians.

Future: Used for events that will occur in the future. Usually "will" or "shall" plus the infinitive form of the verb.
Subject + will/shall + infinitive form (to verb)
Mayhaps I shall someday become a Times Writer officially.

Now here come the hard ones . . .

Past/Perfect: The perfect tense is the past tense. Exactly the same thing. However, it's not the same thing as the past perfect tense (yes, very confusing, I know).
Subject + past participle**** (verb-ed)
See past tense example.

Imperfect/Past Progressive: This one's hard to decide/translate, especially in other languages. In English, it usually uses the following phrases plus the infinitive or gerund form of the verb. This tense involves actions that one used to do, kept doing, was doing, or any repeated actions in the past.
Subject + was/kept/used to + gerund form (verb-ing)
I used to be one of the few who pointed out grammatical mistakes.
However, I kept advocating strength in grammar.
I was doing all that I could to spread the word.
Yo le??a un libro cada fin de semana.

Past Perfect/Pluperfect: Best name for a tense ever. Used for events that began and ended in the past. This is slowly beginning to phase out of common English, because it is more verbose, albeit more correct. Many people use the past tense in place of the past perfect, which is incorrect.
Subject + had + third principal part*****
I had seen that grammatical error many times before.

Present Perfect: It's a bit harder to understand when to use this tense. Basically, anything that happened at an unspecified time before now (the present) will fall into this tense. For example, you can't say, "I have never heard the word 'dawg' when I was a kid," but you can say, "I have never heard the word 'dawg' before." People use the past tense in place of it, again, incorrectly.
Subject + has/have + third principal part*****
I have never known that old school Super Smash Bros. was so awesome.
NOT
I never knew old school Super Smash Bros. was so awesome. (Although it's tempting to write it this way, isn't it?)

Future Perfect: This one is the coolest tense, and the one almost never used. It's called "future perfect" because it uses the word "will" or "shall," but includes the present perfect tense. Hmm . . . See the formation of the tense. =D Used for things that haven't happened yet, but are planned to happen. Yes.
Subject + will have + third principle part*****
In thirty years, I will have been a U.S. Senator for ten years.

Subjunctive "Mood": This was a request from someone, for it is true that you mist learn it, user it, and live it (but not necessarily love it). This is most often used for the "If I only had a brain . . . " cases. Ah, now, there's a catch to this: the statement in question (sentence) has to be assumed false. For example, you can say, "If it were raining, I would run outside with a metal umbrella," because it is not raining now, and thus it is assumed to be false. However, you cannot say, "I would always correct someone's mistake if it were wrong," because you are assuming it is wrong if one is going to correct it, therefore, the statement is not assumed false. (NB: This is the more basic form, the one people usually use wrong, which only covers the "to be" form of the tense. For a full description, feel free to go to www.wikipedia.org and look it up.)
If (usually) + subject + were
If I were just another brainwashed child of the hedonistic generation, I would not be as persnickety as I am now. (Yes!)
I would watch MTV if it was on more often. (No!Wrong, wrong, wrong!)

* The gerund form of a verb is usually the verb plus ???ing, like do + ing = doing. Have + ing = having.
** Am, is, are, was, were, etc.
*** To plus the verb: to shop, to publish, to ostracize
**** Participles: there is a present one and there is a past one. Gerund = participle. So for the verb "to shred," the present participle is "shredding" and the past participle is "shred," as in, "I was shredding the nar-nar when this guy totally shred past me and wiped out. Sick!"
***** Principal parts are hard to explain. Simply put, "I write, I wrote, I have written." Those are the three participles used in English, and they are applied to all the different tenses. (If further explanation is necessary, a y-mail may suffice. Roots can be found in Latin, so it's a challenge. o.O) "I write" is the first principal part, "I wrote" is the second, and "I have written" is the third. This can be applied to all* verbs.

Unless requested otherwise, I shall be writing about nouns in the next article. Ah, but not the "person, place, thing, or idea" definition; no, the different cases of nouns: nominative, vocative, accusative, et cetera. Alas, English does not bother to differ among the cases, but it shall be diverting to explain them all and receive confused, bemused, and dazed looks. Fun, no?

*furiously scribbles ???m into scholarly journals*
Ledyba