How to take printout or print preview of Invoice?

Hi

Could anyone let me know the detailed steps involved in taking invoice printout?. I am aware that with Vf03/vf02 I need to go to Extras->Header->Output. After this I do not know the exact steps either to take the printout or preview the invoice. Please advice.

Are the steps same for taking printout of Credit Memo, Sales Order notifications?

Thanks

Raghu