The Qt coding style is defined at
http://qt.gitorious.org/qt/pages/QtCodingStyle
so let's follow that.

Overall, the basic rule is simple: follow the coding style, and the design and
functionality patterns that are already there. There are patterns for 
getting and setting oFono properties, calling methods and getting the 
method call result, setting the errors, and receiving out-of-band signals. 
Hopefully that should be enough for any remaining APIs which are currently 
missing (some APIs such as SIM toolkit require implementing a d-bus agent for
which there is no example yet).

For any new API that is added, there should also be a test case. Again, try to
imitate existing test cases. It is not necessary to thoroughly test the 
functionality; it is enough to go through all properties, methods and signals 
and check that they work, return sane values and match the actual oFono API. 
The tests should be written against Phonesim phone simulator and it's 
preferred that they should be able to run without manual intervention.