Any of the above will do. However, I'd look at the front of your car first, if you're suffering from understeer. That's what I'd do. If the car is over steering, then I first look at the rear of the car to see what's wrong.
However, I'm no whizz around 4WD cars and I defer to those who know better than I. I've been using the handy little cheat sheets found in the OP of this thread. As a rough guide, it works, or at least makes you think about the individual suspension components and how they affect the cars handling.
Any of the above will do. However, I'd look at the front of your car first, if you're suffering from understeer. That's what I'd do. If the car is over steering, then I first look at the rear of the car to see what's wrong.
Not always with 4WDs - it' the opposite. Alot of 4WDs will understeer owing to the stability of the rear, by loosening the rear the front will turn more.
Going straight to the font and turning that 'up' for more grip, there's a good chance it will knacker your front tyres out quicker, meaning you're straight out of the frying pan and into the fire.
Tuning 4wds you always have to consider babysitting the front tyres for race distance. Loosening the rear is an easy way of doing this and getting the front to turn, without increasing front tyre wear, by tuning the front end first, you're shooting yourself in the foot most of the time as the rear will still be "strangling" the front, you'll have to force the car into the corners, blowing out your tyres early, then the understeer will just get worse and worse and worse during the race.
The front / rear power split can come in very handy to help protect the front tyres though, just shove most of the drive to the rear and set up the rear diff like a rear wheel drive car.
You can tune a car "directly " or "indirectly" - 4WDs it's always worth trying the indirect method first.
