First one: Buy 10 or more tinderboxes at the Varrock General store. You buy them for 1 gp each. sell them at Grand Exchange for 95 gp each. If you buy and sell 10, you got 1k (1,000gp) profit.
Number 2: more experienced you need to be able to telekinesis grab. go to the ditch where you enter wilderness and head west. keep going until you hit the end of ditch where a random church is. there will be some wine on a table. this is valuable wine like 1.7k (1,700gp). But you must use telekinesis grab to get it. Its respawns every 20 seconds so law runes are 300gp and the wine is 1700 so you make 1400 profit everytime. so if you have 27 open slots-- you just got alot of money.
Haven't played in a while but i remember these tricks
i just get imperios ashes and sell them to level 3s for 2k each, sell them bronz armor,i sell monkey bones for 10k saying they give you skill,and also ther ed spider eggs. i say eating these restores full health and makes you invincible. 10k.
I pick up ashes and sell them to n00bs telling them its "Magic Ashes" for around 200cp, lol stupid n00bs, and or i make amour and sell it for around 9,000cp whie ranking up my mining and smithing lv, easy peasy... havnt played in ages tho.. meh my account probally got deleated
members: spin flax non-members:you can get the wine he is talkin about for free if u can kill the monks easily, just kill ALL OF THEM AROUND THERE then grab the wine, it will only take 1 or 2 hp off if u grab the wine off the table! both members and non-members:MERCH! but you can do it induvidually, don't join clans, just buy [for example] ashes USING ALL OF YOUR MONEY... at lowest price in the ge, then, after a day or so or until you buy them) sell them at highest price in the ge! this is how i got all of my 1.7mil (probably about 2mil by now) from starting with 600k! and DEPENDING ON HOW MUCH MONEY YOU USED TO BUY THEM you can earn anywhere from 5gp to 100mil!
I havent played in a while but member can fight greend dragons (lvl.79 I think) and sell each bone for 5k....and non members, make clay into wet clay(use clay on bucket of water).... ;D