FORMATTING:

  -To get bold text insert the text between asterisks....i.e.,if you want to make the word strong bold type *strong*.   -For italicized text insert it between underscores....i.e.,to get roman in italics type _roman_.

  -to insert special characters like §© open windows->run type charmap.exe select them their and copy paste in the message window.You can as well copy them from somewhere else..but charactermap is the right place I suppose.

  -EMOTICONS -many people don't know

	<3
It's a monkey!	:(|)
Rock out.	\m/
	:-o
	:D
	:(
	x-(
	B-)
	:'(
	=D
	;)
	:-|
	=)
	:-D
	;^)
	;-)
	:-)
	:-/
	:P

Keep in mind that if you send an emoticon to someone who isn't using chat in Gmail, it may not display properly. 

 source:official Gtalk help.

CUSTOMIZATION:

   -To change the colour of your Gtalk you can use GTALK COLOR CHANGER created by WUMPUS 

   -To add many features to the Gtalk like

smileys like yahoo messenger,dynamic status message change,locking etc...etc .,use EXTENDED TALK created by MEO n VIKKE 

   -To run multiple instances of Gtalk on a single computer on the shortcut icon rightclick->properties->shortcut->target

in the target to the path given add an extra string [space]/nomutex.[space] means u have to press apace bar once.Take care not to erase the already present path.Just add the string at the end of it.

   -To show your current music track being played in winamp in your custom message select "show current music track" in the drop down menu of status message.

   -Use themes to change the appearence of chatwindows.

OTHER: 

  -Gtalk file transfer can be used to transfer infinite number of files whatever their size may be freely.If you are behind a firewall 

• Enable UDP connections to anywhere on any port; or

• Enable TCP connections to anywhere on port 443.

  -Gtalk along with voice chat also offers you with voice mail wherein you can send offline voice messages to your friends.To send voice mail in your chat window click the top right button to get dropdown menu with send voice mail in it.The voice mail will be sent to the inbox of the receipient.