For the first 5 picks, pick the highest valued cards. This means stuff like Piloted Shredder, Truesilver, Consecration, Dire Wolf Alpha, Blessing of Kings, Murloc Knight, so on.
After that, for the next 10 picks begin constructing as close to a core as you can manage. This means rounding out your curve and ensuring you still have tons of value to go off of.
For the final 15, pick for cohesion. This means picking up more mechs if you have mech synergy cards, or more murlocs, or whatever else.
At least thats what I've seen.