Super heat, sub cooling, and Coil cleaning??

Just finished up the computer part of class on super heat and sub cooling. Seems like every other page said to make sure condenser and evaporator coils are clean before taking pressure readings....dirty coils make for inaccurate readings...since so much emphasis was put on clean (cleaning ) coils before taking readings I wanted to ask those of you who actually are out there working???

Do you all clean coils first or just do a visual and if coils look "ok" do the readings? Have you all noticed a problem with getting accurate super heat / sub cooling pressure readings with the coils you run into day in and day out at the average house?

I'm sure cleaning coils is not free so do you itemize it on the bill and explain to the customer that you had to clean the coils before you could accurately trouble shoot the system or just include it as a cost of checking the system??