Some sortcuts on symbian phones

Press and hold the Menu key to open the application switching window, where you can *duh* switch between applications.
If a program hangs and you can't shut it down, select the application in the
application switching window and press 'C' to kill it. It's also a faster way to exit programs.

Turn on/off the "click" sound made by the camera by selecting the 'Silent' profile or by turning warning tones on/off:
Menu > Profiles > "select your activated profile" > Personalise > Warning tones > On/Off.
(This also effects the sound of Java games and apps).

To change background image go to:
Menu > Tools > Settings > Phone > Standby mode > Background image > Yes > "choose an image".
The best size for background images is 174x132 pixels.

Only got blue, green and purple in your 3650 colour palette?
This free app adds 3 more colours: Palette Extender.

Display an image when someone's calling:
Menu > Contacts > "select a contact card" > Options > Edit > Options > Add thumbnail > "choose an image".

Add a personal ringing tone to a contact:
Menu > Contacts > "select a contact card" > Options > Open > Options > Ringing tone > "choose a ringing tone".

Delete all messages from your Inbox at once:
Menu > Messaging > Inbox > Options > Mark/Unmark > Mark all > Options > Delete.