choosing the transistor

[Adhith]

 :-[Hello everyone..
As a part of my project vu meter project i need some help on choosing a transitor for its switching.What I'm looking for is either a 5V or 12V at the base emitter junction should trigger a 12 v through the collector. The output load current won't be greater than 500mA. So which transistor should I use ??I also need help with choosing the base resistors for the transistors. So could anyone help me with some suggestions??