How to navigate to your .Minecraft folder

On Windows:

Method 1:
Go to the start menu and enter %appdata% in the search field.

 

Method 2:

Open Explorer and enter %appdata% in the navigation bar:

 Both of these methods will give you access to the .Minecraft folder.

On Mac OS X:

Press Shift + Command + G and enter /Library/Application Support/minecraft

Note that in OSX the folder is called minecraft and not .minecraft.

On Linux:

Enter your file manager, navigate to your home directory, and press Control + H. This will reveal the .minecraft folder.