As you have probably heard before, Aviate, Navigate, Troubleshoot, Communicate.

Follow that order and everything will be fine. Now, with the whole "do I tell ATC or not, or to declare or not to declare an emergency..."

Think of it this way, I am sure you would rather be on the ground safely with the FAA and other pilots saying you shouldn't have declared an emergency, than be dead having other pilots saying that I should have declared an emergency.

Just fly the airplane, if ATC yells at you for not saying anything, all you have to say is "I was focused on flying the airplane, and not killing myself." If they believe you should communicate before flying the airplane, they can go to hell.

If I was 500 AGL trying to put a plane in a field or a road, the last thing I would be thinking of is if declaring an emergency will draw good or bad attention on me and the operation I am conducting. If you think its an emergency, and you are flying the airplane before communicating, declare it - or atleast say mayday mayday mayday, N##### 3 miles east of whatever, engine quit, off field landing. Just be very short and clear, and fly the airplane, don't worry about all that!