The first thing to know is, that when it comes to choosing the perfect vase, size matters. The general rule of thumb is that the length of the flower stems should be no more than one and a half to two times the height of your selected vase.
As well as the height of the vase, look at the opening. If the neck is too wide it might not provide enough support for the stems and you could lose the shape of the arrangement. Too narrow an opening and it could constrain the design of the bouquet or even damage the stems.