A princess cut diamond is probably one of the most popular cuts available. Principally due to the brilliance of the cut and how it shows of the diamond so well.
The original cut was called the Barion cut and was invented by a South African, Basil Watermayer around 30 odd years ago in Johannesburg and the princess cut originated out of that, mostly when the patents ran out some years ago (Diamond cuts can be patented and are worth a considerable amount of money).
A princes cut diamond is a square version of the round brilliant cut and has improved faceting which gives it a much more brilliant sparkle.
Princess cut diamonds should be made from deep cut stones. These make the best princess cut and lowers the maximum weight retention and gives a better balance.
Usually inclusions are less visible and coloring is less visible also.
The points of a diamond are the weakest areas and this applies to princess cut diamonds also. A princess cut diamond should be mounted so as to protect the points therefore. Usually when they are being mounted there can be some force required to set them and this can mean there may be some damage when they are mounted. Usually this is fixed with some further polishing but this adds delay and cost to the piece.
Have any princess cut diamond you are getting set examined for any flaws that might have occurred in the setting. One should always ensure that the four points are protected when set so they do not get chipped during normal wear. (believe me, it can happen!) and that they are still present and have not been chipped when set.
The minimum recommendation for buying a princess cut diamond would probably be:
Cut: Very Good
Depth Percentage: 58-80%
If you are on a budget then this may be outside your range then you can still locate a diamond that fits in the following range:
Depth Percentage: 56-84%
You can of course go cheaper but that is not recommended. The beauty and value of the stone is important if you want something that looks nice and like a diamond.
Keeping in mind the above will help a long way to you having a very nice princess cut diamond which you can treasure for years to come.