[Sonoboy]

I guess I'll take a shot at this.

Should I mark contacts in narrowband (most of the time towed array contacts) if I cannot get a tracker in broadband or should I wait until the contact is visible in broadband before I mark anything in narrowband?

You should mark contacts in NB when you can't mark them in BB. Then when the contact is visible in BB, unassign the tracker and reassign it in BB. The advantage to marking a contact in BB is to get DEAMON information.

Which frequency should be marked in narrowband, the strongest ones (which are shared by many platforms) or rather faint ones (which makes the difference between platforms)?

It would depend on the array used. For the towed array (which is good for low frequencies), mark the lowest frequency line (the left-most one). The sphere array is good for higher frequencies. You should mark the strongest lines.

Do you get what I mean?

Yes.

Oh and do you mark both contacts (true and ambigous) on the towed array before you make a turn to resolve the contacts and delete the ambigous contact afterwards, or do you make turn first to find out which contact is the true one and then mark it?

Nothing wrong with that. That just depends on your style. I will sometimes do that when I'm marking mirrored contacts in NB.