You will need to consider the materials used for construction, the size, and the overall quality of the corner cupboard you are considering in order to choose the best one. It helps to decide ahead of time where you will place the corner cupboard and what you will use it for before beginning your corner cupboard search; this will give you a better idea of what to look for and how big of a unit to purchase. Consider price, too, and decide ahead of time if you want a new unit or if you want to search for an antique unit.
Antique corner cupboard units will likely cost much more than new units, and they may or may not require some refurbishing. These cupboards will add a unique aesthetic and a conversation piece to any room, but antiques do require some care and maintenance, and older cupboards may need some refurbishing to get them in working order. Wood can warp, joints can loosen, and water damage can occur, so when considering an antique corner cupboard, be sure to either budget for refurbishments or prepare to do any refurbishing work yourself. Once the unit is ready for use, it will often be worth the effort and cost.
Consider whether you want a corner cupboard with an open face or solid doors that close. Some doors feature glass windows to allow the items inside to be seen while still protecting them from potential damage. Many people store good china in a corner cupboard, so doors with windows are ideal for showing off the china while still protecting delicate pieces. Solid doors are available as well if you would prefer to let the cupboard itself be the focal point, and open face cupboards with no doors will allow for an unobstructed view of the contents of the cupboard.
The cupboard should be made from high quality materials if you intend to use it as a focal point or as a unit for holding heavy or delicate objects. Look for solid wood cupboards; hardwoods are best, though other woods are good choices as well, as long as they are durable and resistant to water damage such as rot and mold. Some woods will cost more than others, particularly naturally attractive woods such as cedar or teak, or woods with a prominent grain such as oak. These woods tend to be quite beautiful and durable, but expensive.