a) often the way I discover about the other programs/things that are similar is the fact that they also appear in the same drop down menu.
b) memory. Often the name of the item is not something I recall, but I remember the shape/color of the icon, or the association with the location in the menu
c) namefail. These things (at least how it works in Ubuntu 11) suck at finding the actual program. Some programs have multiple names by which they are known and they don't show up when you type the more common one. Google Earth is a good example. Or some - just don't show up at all for some reason.