These are the most commonly early frequently asked questions. This page will hopefully fill in some gaps with some advice when you're just starting out. These are the tips that bridge the time from "Just Learning" to "Novice".
Microstrip, stripline, and future physical transmission lines have a "properties" component in the toolbox. It's really a variable block with the properties common across a microstrip circuit (permittivity, dielectric height, etc.) This element fills in a lot of properties that typically don't change across a board, so are left as variables in the components themselves. You should add the properties component before adding other devices (not required, just a suggestion).
When in doubt, open the console window... the error messages often suggest how to fix the problem.
If a component's reference designator is turned off, then the element is ignored in the simulation- this is convenient if you recognize it and painful if you didn't realize the part's missing. The console will contain a list of parts which are not part of the simulation as of version 4.4.3
Components need to have unique reference designators. Use "Special->Generate Symbol References" to automatically handle this. The console will display a warning if parts have not been defined.