Oy, this one gives me a bit of PTSD, but I totally agree these discussions are so important!
As someone who has been through a major injury and sustained significant head and neck injuries, I can add my 2 cents to the neck strengthening topic! I was also very active in lifting beforehand and heard more than once that strength was the reason I survived my crash and am riding and walking today - so strength training is SO important for all riders! For already active folks, exercises I found very effective are:
- farmers carrys with shrugs,
- turkish get-ups (with heavy weight once your form is good),
- high rep shoulder work including shrugs and presses; and
- bent over exercises (like rows) that force neck extension and stability while other muscles are under working hard.
Chin-tuck and chin-tucked rotation exercises on all 4's (i.e. hands and knees) are great, especially when recovering from a neck strain - you could add a light resistance band around the back of the head once the normal chin-tucks on hands and knees feels easy.
Also lying on your back simply lifting your head up (but keeping it parallel to the floor) while applying using light pressure from your hand on the forehead helps engage the back of the neck.
Form and posture are always key, especially with the neck. Those, along with pilates, were pretty key to getting my neck back up and running again and also helped build the muscle that protected me in the first place!