As requested, tonight's workshop will be covering tenses! This workshop was a little hard for me to write - tenses are simple enough once you understand them, but explaining it to others is surprisingly difficult. I'll do my best, though! And credit goes to the Gregg Reference Manual for helping me put it into words.
I won't be talking about the future tense, because you won't really find narratives written in future tense. If you have any questions about future tense, however, go ahead and ask them in the comments.
Since past tense is the most common tense used in fiction, let's start with that. Here's a passage written in past tense:
As the skies began to cloud over, Jo sat on the couch and turned on the weather channel. There had been horrible weather all week, and she had read a story in the newspaper about possible tornadoes in the area.
"What are they saying?" called her mother from the kitchen.
"Nothing yet!" Jo yelled back. "They're still talking about the Midwest!"
And now here's the same passage in present tense:
As the skies begin to cloud over, Jo sits on the couch and turns on the weather channel. There has been horrible weather all week, and she remembers reading a story in yesterday's newspaper about tornadoes in the area.
"What are they saying?" calls her mother from the kitchen.
"Nothing yet!" Jo yells back. "They're still talking about the Midwest!"
(As per Allamorph's suggestions, I changed the passages a bit to make them simpler. Thanks, Allamorph!)
So as you can see, tense is expressed primarily by conjugating the verbs differently. Each and every rule of verb conjugation would take way too long to review here, there are thankfully many English teachers that have already done the job for me.
There are, however, a few things I want to point out in the above passages!
In the past tense passage, look specifically at this sentence: There had been horrible weather all week, and she had read a story in the newspaper about possible tornadoes in the area.
The verbs here, "had been" and "had read," are in past perfect tense. The Gregg Reference Manual defines past perfect as "a tense indicating an action that was completed before another past action." So Jo is watching the news in the past, but the horrible storms and the news article Jo read are even further in the past.
When writing in past perfect tense, the writer always has to make sure to use the correct form of the verb. Many people attempt to use the normal, past tense form of the verb in a past perfect sentence. Take these sentences, for example:
I have broke the dish.
The dress has shrank.
Prices have rose again.
These are all incorrect. The correct forms would look like this:
I broke the dish. / I have broken the dish.
The dress shrank. / The dress has shrunk.
Prices rose again. / Prices have risen again.
The sentences without have/has are normal, past tense sentences. The ones with have/has are past perfect. Make sure to double-check that you're using the correct form.
Likewise, look at that sentence in the present tense passage: There has been horrible weather all week..."
"Had been" becomes "has been" in the present tense passage. This is present perfect tense, which is used when an action began in the past, and is either ending in the present, or continuing into the present. The horrible weather began earlier in the week, but it has continued into the present.
When writing, the most important thing to remember is to stay consistent. I've seen people begin with a certain tense, and then swerve back and forth from one tense to another. Decide which tense works the best for your story, and after finishing a piece, read through it again carefully to make sure you didn't switch midway.
Also, remember that situations where past and present tenses mix do exist:
I watched in horror as Chris drove onto the porch. He has always been a bit of a drunk.
Here's a combination of past tense and present perfect tense. This would sound awkward from a third person POV, but since the first person POV is more familiar and less formal, the narrator can share details from the present, like Chris' continued drunkenness, without the reader questioning it.
And another:
Millie raises her hand high in the air. Since she read the assigned reading last night, she already knows the answer.
This is a combination of past and present. The verb is conjugated as "read" and not "had read" because past perfect takes place before another past action. Since Millie is raising her hand in the present, a simple past tense verb is sufficient.
Questions? Additions? Corrections?