If you get diamond of great value or anything you can get a lot from mining O_o Otherwise you don't get many plats

Basically you get 999 stamina, go to the mines, and mine nonstop until you have like 100 stamina. :p

Of course getting diamonds/diamonds of great value would basically hand you that money all by itself. I feel the best way to make money is just walking around the main island and picking up stuff monsters dropped that no one has taken. I've gotten lots of items simply by walking along the paths and seeing potatoes and mandrake roots and stuff just sitting next to a monster.

Mining is guaranteed though.. you can't always have good days while scavenging for dropped items.

That's a good point, get a detect items scroll and do stuff like that.