People generally find good items from investing a lot of time and fg into the game. Most people generally find good items by welling them or finding them in the Arena. Catacombs are not known for its leet drops.
As for what is welling, welling is when you drop a non-magical item into the well and after defeating that monster the item is now magical+ and you have chances for secondary drops. Be warned though welling can be very difficult
but investing in the proper gear will give you a better success rate
Most of the guides you will need can be found here
http://forums.d2jsp.org/topic.php?t=18560908&f=272Let me know if you have any more questions.