Choose a container that will complement the shape and color scheme you have in mind. If you are just starting out, go with a traditional size vase __ not too tall, and not to squat. As a general rule, your container should be about one_third to one_half the size of your finished arrangement. So, for a vased bouquet you'll need mostly flowers with longer stems. A smaller bowl or basket is fine, too. You'll simply have to cut stems shorter and may need floral foam to help position each bloom. It helps to start with the simpler designs and work your way up, and a vased bouquet is often recommended for a first project.
The judging of the designers work is extremely subjective. Each person that sees the design will make their judgement based upon personal preferences for design styles and flower choices. There is no set of common criteria used in making decisions about whether a person likes or dislikes a floral arrangement. In fact, there is not a standard criteria list which is used by everyone. To further convolute matters, judging actually comes from more than just one or two people _ they come from the recipient, the customer who placed the order, and third party observers (anyone else who sees the arrangement). Therefore it is virtually impossible to please everyone with each design that is created.