What's the best way to secure tickets up front?

I want to travel to London and catch a game some time in February - April.

The only options I can find from Norway to purchase currently costs around £700 per ticket.

Is it really that expensive? I just have no clue about prices or how to purchase tickets. As I’ll have to secure flight seats and hotels soon to get a good deal, I’d like to secure game tickets up front as well.

How do you do it? Do I register as part of some official game club? Do I have to wait in a queue? Do I have to pay with my liver if I want to secure tickets up front?