Use "~~~~" to sign your posts on a discussion or debate page. This leaves your username and timestamp with the comment you have made.
To change your signature - go to "My preferences".
If you would like to use color in your signature, use the following code:
Use this color mixer to find your desired color code here
Replace the 4d4d4d with the color code.
<font color="#000000">username</font> --> black
<font color="#ff0000">username</font> --> red
<font color="#ffff00">username</font> --> yellow
<font color="#0000ff">username</font> --> blue
<font color="#00ff00">username</font> --> green
Superscript - <sup></sup>
Subscript - <sub></sub>
If you don't have tildes on your keyboard, you can use the signature shortcut.
When you are typing on a talk page, you'll see a bunch of light blue buttons, like B I etc. The 10th button (between the red circle and the horizontal line) inserts your signature with timestamp. It's the same as you typing --~~~~ but it's a little easier.