This Question came to me from a Mooney Pilot I flew with a while back:
I plan to fly to northern California, is it recommended that I establish flight following during the entire extent of my flight?  What airspace will flight following allow me to fly through?

Answer:
I would highly recommend using flight following as much as possible.  Flight following or radar advisories as it is frequently called will allow for an easy transition though some airspace. ATC serves as an additional pair of eyes looking out for traffic and also they will be there to assist you in case of an emergency.  Keep in mind though that you are not always able to get flight following for several reasons.  In some areas, terrain can affect radar and radio coverage and services may not be available.  Also there is a chance that ATC services will not be available due to a controller’s workload but this is a very rare occurrence.  In this situation a controller may ask a VFR pilot to ‘remain clear of class B, C and D airspace and call back in 5 minutes.’  From my experience I would estimate that services will be available greater than 95% of the time.  In most cases controllers would rather be providing services to VFR pilots than not.  Communicating with VFR aircraft will allow them to coordinate IFR traffic much easier than if they have a random VFR plane flying around off frequency.

Potomac TRACON Facility

Receiving flight following will only allow you to transition class C airspace without further clearances or clarification.  Flight following will not allow for automatic clearance to fly into class B or D airspace.

Before flying into class D airspace ensure that you are in fact cleared into the Class D or have the means to attain a clearance.  The first option is to get a ‘hand off’ to the class D control tower well in advance in order to give you time to make two way radio contact. Don’t count on the en route controller to give you this hand off in time.  If necessary, ask for a frequency change!  Another option is the en route controller can call ahead via a land line to the class D facility and arrange for a transition.  In this case thepilot would stay on the en route controller’s frequency.  Lastly, some control towers have letters of agreement (LOIs) with the enroute controlling agency that will allow for a specific arrangement to allow pilots to transition the class D airspace.  All this might sound a bit vexing, however the upper limits of Class D airspace is usually 2500′, so most VFR cross country routes will take pilots above this airspace.  Always be certain to check your chart for any conflicting airspace prior to departure.

Class Bravo airspace gets special treatment since it always requires a specific clearance to enter.  Prior to entereing a Class B airspace a pilot must recieve a specific clearance.  A Class B clearance should specify the route to be flown and also the altitude assigned through the airspace and be read back clearly by the pilot. Under most circumstances a class B clearance is initiated by first establishing flight following with a TRACON (Terminal Radar Approach CONtrol) facility and then making the specific request for a transition.  All class B TRACON facilities seem to have their own unique personalities. Some seem to operate like an iron curtain, where others will roll out the red carpet.  It certainly never hurts to ask for a clearance but as a general rule I don’t plan on transitioning haphazardly through Class B.  If the Class B airspace becomes to daunting for transitioning VFR pilots there are generally transition routes with unique rules and routes to be flown.  Remember, you and you alone are responsible for your safety but flight following is certainly a useful tool to help you succeed!