**how to tell your employer you are leaving *?

ok so the thing is i am one of the top people at my firm. no im not tooting my own horn..but this is why i need advice...i will be quitting on friday...or tuesday....but i dont know how to go about doing it..no one at my workplace has a clue..and this will be a major bomb...i love my current job but im bored,overworked, and underpaid...there is no room for negotiation because the new firm is paying me $15k more..and i know they wont hike up my pay that much...anyway how do i go about doing this....this firm has done a lot for me and i owe them big...and im definitely not going to leave at bad terms...how will my manager react to this..when they are not expecting it at all...and think im the kinda person who would stay there forever.....