Mods won't work on Minecraft?

So I've tried to install mods onto Minecraft many times- yet they have never worked. I have the official paid Minecraft, and a Windows 7 computer tower that's around 2 years old.
I follow the instructions as best as I can- and yes, I deleted the META-INF folder.
After I install the mod and all that stuff, I open my Minecraft and it works perfectly, yet there are no mods in game. It works as if nothing has been modified.
Any help is greatly appreciated!

Firstly, there are many video tutorials.

However, if you're looking for something easier than download an installer such as minecraft forge or modloader. These will load mods for you and there's basically no installation required. I use them all the time and they work perfectly with as many mods as you like. Just make sure you have the latest installer and the version of the installer matches the version of the mod you have downloaded.

If however you do not want to download these installers try the following:
Download the mod
Locate your.minecraft folder
Scroll to versions
Drag the mod into there
Launch minecraft
Create a new profile using the version you just installed by going to the "versions" section in the profile editor and selecting the mod.
Done!

**Note that you will only be able to run one mod at a time using these instructions, hope this helps!