

Super Uniques are very good for this since they can have predefined TC that can be a lot lower than there mlvl, reducing the number of items they can drop while keeping there mlvl high so they can drop as Unique/sets. So the questions you need to answer to get the item you want is what is the item level of the item you want, what TC is it in and where do I find monsters that are above them. By keeping the max TC of the monster your slay as close to the TC of your desired item, you can exclude unwanted items from even having a chance of dropping and there for increase your chance of getting the item you want. So if you want to increase your chance of getting an item you need to kill monsters with higher mlvl than the TC of the desired item and with a mlvl higher than the ilvl/qlvl of the desired item. If the mlvl is lower than the ilvl of the unique/set item it tried to spawn it will spawn as a rare with triple the amount of durability instead. Set and Unique items can have higher item level (ilvl, some times also refereed to as quality level/qlvl) than TC, before such an item can drop the mlvl needs to be equal to or higher than the ilvl. Once the item has been chosen a check for the quality of the item is done, this is where your Magic Find (MF) helps.

Other items(ring, amulets, jewels, charms and runes) work a bit different, see the above links for more information on them. In short for weapons and armors when a monster dies or a chest is opened the item that drops is picked from a Treasure Class (TC), the TC has to be equal to or less than the monsters level(mlvl). There is a good guide here for how items are generated. Maximizing your chances of a specific item is a complex set of events when an item is generated.
