The fastest ways from level 74 to 99 would be:
Firstly: Buy a dwarven cannon, use it under the lighthouse (Must do Horror from the Deep), wear your best defence armour, barrows is reccomended and cannon dagganoths until you get 80-85 range. If you have high defence (70+) they wont hit you much.
Second: Once you're done getting to 80-85 range, you can start chinning... You'll need to have completed Monkey Madness.
Every time you go, you'll need to bring around 1800 Red Chinchompas, your best range armour (Defence is irrelivant, only thing at matters is range and prayer bonus as you'll be melee protecting), ring of life is suggested for first-timers. in your backpack bring 2 anti poison potions, 1 shark, 4 range potions, 20 prayer potions and a teleport tab to anywhere safe.
To get there, go to ape atoll, once you get there, walk through the jungle untill you see a dungeon, turn your melee protect prayer on, you wont turn this off until you leave, be sure to use prayer potions wisely because if your protect goes out for even a few seconds, you could die.
Run through the dungeon until you reach some skeliton monkeys. once you get there, throw red chins at them.. the red chins hit up to 9 targets and the monkeys spawn from their own bones, so if you stay there long enough, you'll always be hitting over 9 of them..
This method will get you around 170k exp/hour at level 80, and up to 250k/hour once you're near 99.
These methods together will cost around 50million. I did it this way only because I had money, if you're not willing to spend that much, I suggest buying steel darts, and throwing them at whatever monster you want drops from.