I'm a causal player, which means I don't really care about xp/hr or gp/hr, I prefer afk style training, and I want get every task done as fast as I can.
I always get task from Morvran, the elf.
Remember to carry slayer VIP ticket when getting a new task.
I always choose regular task over slayer challenge.
I solo most of the time, although you might want try co-op if you can.
Mighty slayer helmet is a must, get this.
Get all the slayer items on tool belt.
Turn on the slayer counter.