Grand Exchange - item investments!

There are different methods to determine whether you should invest in an item or not, but I usually look at up-coming updates. With the return of the Wilderness and with the PVP update you were able to pronounce alot of items used during PK'ing would start to rise (including armour/weapons, food and potions etc).

You can also determine whether you should invest in an item or not by watching the Grand Exchange graphs closely.

For example:
​One day an item falls 20k, the next 15k, the next 10k, 5k, then drops 2k, rises 2k, rises 15k, rises 30k and so on. The best time to buy this item would be at drop 5k. This is because you will be able to get it for under the medium price and it gives you much more profit.