Use BB Code

BB Code is a series of tags similar to HTML that allows one to format messages, text, and links. However, this code is very simple and will not break the layout of a forum page. BB Code may be limited in certain areas of the forum, so be sure to establish any restrictions.

Bold / Italic / Underline : [b]bold text[/b], [i]italics[/i], [u]underline[/u]
Color : [color=blue]blue text[/color]
Size : [size=1]size one font[/size]
Font : [font=Times New Roman]times new roman font[/font]
Left / Right / Center : [left], [right], [center]
Email Linking : [email]me[MENTION=40890]ema[/MENTION]il.com[/email]
URL Hyperlinking : [url]www.website.com[/url]
Images : [img]url of image here[/img]
Quote : [quote]quoted text[/quote]
Stop BB Code Parsing : [noparse]BB Code
Attachment : [attach][/attach]
Bulbapedia link : [bp]Cilan[/bp]
Strikethrough : [s]slashed text[/s]
Spoiler : [spoiler]text inside spoiler[/spoiler]
Subscript : [sub]
Superscript : [sup]
Wikipedia link : [wp]Pokémon[/wp]

Please see this for a more detailed guide.