But having a significant history of flights with the airline will probably help.
So why did I not manage to get the jump seat the summer I spent as an LNO in the Middle East taking 3-4 Herc flights a week?
In all seriousness, I think it is luck of the draw. I have never once managed to get an upgrade and the only time I have ever flown business class with MOD was when PJHQ left it so late to book the tickets that business class was the only option left. The only other time was when I had to travel on one of the smaller business airlines when I needed to get to Lossie and as the ac was too small to have more than one class of seating so it was business class nose to tail.
My parents on the other hand seem to have upgrades thrown at them. I remember hearing of one occassion when they were coming back from Rome that they were in the queue to check in and hadn't even got half way to the desk before an Alitalia rep extracted them from the economy class queue and upgraded them without their asking. And more undemanded upgrades have been forthcoming since then. It might almost be worth at least taking them to the airport with me next time I go away!