Thieving
Thieving is a good way to make money when you are at a higher level. At the beginning you may think you are making no money at all, but it will be rewarding when you are a higher level as you'll be raking in the money.
When thieving you should thieve the best thing your thieving level will let you. If the npc is a high level you should bring some food just in case you get stunned
High alchemising
You need level 55 mage:
The best things to high alchemise is gems, most likely diamonds and bows as well as steel plate mails.
Mining
It is best to have a mining level of 40:
In the beginning you should mine copper and tin till your level 20. After that you should mine iron till level 30 then you should start to mine coal till you're able to enter the miner's guild. When you enter mine anything from coal and above, but when you are able to mine coal mine it from the wilderness. The ores you collect , you should keep it or sell it.
Smithing
It is a good way to make money. You need ores to smith:
Smith the best bars you are able to smith. With the bars you can sell them or smith them into items to then sell on (only recommended on rune items or if your going to make arrows).
If you've got lvl55 mage and lvl48 smithing you should get 2000 iron ores and 4000 coal ores (or a 1:2 ratio between iron ores and coal ores) then smelt them to steel bars then to steel plate mail. High alchemy the plate mail or sell them. If you use the amount of ores specified you will make between 392k-480k
