um..well..i only have 70 range,but i've watched quite a few 99 range videos,and read alot of guides. here are some good things to train on: yaks(use bronze knives-i got from 40-70 range with them in just over 2 weeks) they can be found in neitiznot,which you gain access to after starting the fremennik isles. :)
I've heard that fire giants are also good,but you should only train on them once you have 75+ range :P i cant remember where you find them...although it's after the waterfall quest i think =]
also,it's definitely worth wearing a sacred clay coif,double the experience! :D so if you killed a yak you'd get 200xp,rather than 100 xp ^-^ so get quite a few of them from stealing creation.
I would recommend going to the yaks,since they're only level 25,and bronze knives work very well on them :)
(i think you can train on ankous in the stronghold of security too..but i'm not sure on that one :o)
if this doesnt help you can always look for guides :) good sites are: tip.it,sal's realm of runescape,zybez,runescape wiki,and so on :P
good luck on 99 range! :)
played runescape for 3 years,i have lots of friends with 99 range,and i've read lots of guides :)