Okay, so I read through the first tutorial and noticed that it might be good to explain how you use these settings together.
So I thought I would give you some examples how aperture, shutterspeed and iso works together.
I will try to explain it as simple as I can, but I need to go through some technical stuff first, sorry…
I use the metering system on my camera to see if I am under or overexposing my photos.

(The I is in the middle which shows that the photo isn´t over or underexposed)

Which always isn´t the best way, but I think it works most of the time.
The problem is that the camera calculates the light coming from the subject you are photographing but it can´t see the actual light which is on the subject, because you are probably standing a few meters from what you are photographing.

There are usually 3 ways or controlling how your camera is metering the light:
Multi-Segment Metering
This one splits the photo in to different segments, then checks all them, then gives you the light exposure from average of them all.

Center-Weighted Average
This one pretty close to the spot metering, it takes most from the middle and then it takes a little from the rest.

Spot Metering
This one just takes the light exposure from one spot.

This is the icon, where you can see which one you are using at the moment:

To really get the right light exposure you should have a handheld light meter.
This way you can go up to subject and see what the light exposure is where the subject is.

But as I said, I have never used one of these, and I think I´m getting ok pictures…
I mostly just use the Multi-Segment Metering and rely on it.

So NOW we can start with the examples:
Shooting in when it´s sunny outside:
This can be as much trouble as shooting in dark places if you don´t have the right settings.
The biggest problem is that you will blow out the sky, this is something I see on a lot of photos.
The best way to fix this is changing your aperture.
Now three “main” options:
I will mostly go in to how you shoot with Manual settings, but you can shoot with the TV or the AV settings too.

Some basic “rules”:
The first rule is called the “sunny 16″, which means that you should have
Your aperture at f/16
Your Iso at 100, (iso 100 is good in bright sunshine).
Your shutter speed at 1/250 sec

You can have your aperture at a higher aperture too, let´s say f/8.
The difference is that now your lens is letting in more light, which means you have to start using faster shutterspeeds, (something around 1/500sec)
If you are using too higher aperture like f/2.8 your camera might not be able to get the shutterspeed fast enough, which means that your sky will get overexposed, or you will start jumping really big steps, like 1/2000sec to 1/3000sec and there is nothing in between…
Remember to look what your exposure meter on your camera says, is it under or overexposed?
Time for the next example.

Shooting indoors/low light
Now you need to do the opposite from what we just did.
The higher aperture you have the more light it will give you for example 2.8 is a pretty high aperture.
Now you have to start making decisions.

1. Higher iso, will decide how light sensitive you photos will be.
The higher iso amount, the faster shutterspeeds you can use.
But remember that if you are using too hight amount your images will become grainy.

2. Change your aperture.
This is where your lens comes in to play.
Most lenses has different aperture values, for example: f/1,8 or f/3,0 - f/4,5.
f/1.8 means it´s really good to take in low light, because it can let in so much light.
The f/3,0 - f/4,5 are usually on zoom lenses where for example a lens that has the range of 24-70mm, which at 24mm it can give you the aperture of 3,0 and at 70mm it can only give you the highest aperture of 4,5.
And oh, 3,0 - 4,5 doesn´t mean you can´t choose lower apertures, those are just what the highest aperture the lens can have.
So you can still choose f/22 if you want…

3. Change your shutterspeed.
If you are shooting moving cars and you just want those car lights to be visible you can use long shuttertimes.
But if you actually want to get the photo of the car, and you are in low light, you are starting to get in to trouble…
If you take a really fast shutterspeed, even though you have a high iso and a high aperture, you will probably not be able to get the car, you will get a black photo because what the camera is doing is recording the light, and when there isn´t enough light to record it will just give you a black or very dark photo.
Even when you are trying to shoot indoors you might have big problems trying to photographing something that is moving.
But don´t worry that´s when the flash takes its part.

Only problem is if you are shooting with a flash that is on your camera, it will come directly on the subject and overexpose most of the image.
That´s why I´m using an external flash, but that´s a whole other story…