There is a great number of different screen resolutions out there. Bellow you can see various sizes, from the oldest 96x54 to the new 240x320. And these are not all of them. A more complete list of handsets and their screen resolutions can be found at MIDP Benchmark.
So how can a Java ME application behave properly on so many different handsets? Use the standard UI classes: LCDUI.
Ok, LCDUI is not appealing. Programmers do not control the layout, or even the colors, of the elements. Vendors implement the look-and-feel as they like. But where Java ME is supported, there you will find Lists, Forms and Dialogs.
A good approach is to have only two Commands per screen. One of type OK (positive answer) and the other of type Cancel (negative answer). As manufactures do not mix these concepts you will end up having one command on each softkey.
Another benefit to use LCDUI is that it does not add to the application size.