Preflight planning is a very important element of any flight and especially so when going on a cross country flight. There are a number of items to be done in preparation for a VFR cross country in such a way that nothing is overlooked and the intended flight is done as safely as possible.
When flight planning you will sometimes cross controlled airspace, the manual below contains some useful tips for doing that safely.
Eurocontrol Guidance Notes
Excerpt from the document:
The Rules of the Air state that clearance must be obtained before an aircraft enters controlled airspace. All aircraft wishing to do so must file a flight plan, either on the ground before flight, or in the air (calling on the ATC frequency), and the air traffic services involved must receive the request a certain number of minutes (usually 10) before the expected time of entry.
Your license and aircraft equipment must also allow you to enter the particular Class of airspace in the conditions prevailing (VMC or IMC).
To continue reading see the pdf below: