Flight Information Service (FIS)

To contact FIS, you must first know:

Which facility provides FIS in the area you are flying. This information is in the Aeronautical Information Publication AIP for your country, and in electronic flight planning systems. Different countries may have different FIS providers for different areas.
Which frequency to use. FIS frequencies are published in the AIP and in flight planning tools. They are usually unique to a region.
What service category you are entitled to. Not all pilots are entitled to all FIS services. VFR pilots are entitled to the standard FIS package, which includes position information and non-urgent traffic information. IFR pilots receive more detailed services. Commercial operators may receive additional services.

VFR pilots in uncontrolled airspace are entitled to basic FIS, which includes:

Receipt of your position report
Provision of relevant traffic information
Provision of relevant weather information
General flight safety information

In many European countries, this service is called "FIS" or "Basic Service" when the facility is not providing radar service. When a FIS facility has radar capability and is providing radar service alongside FIS, the service is often called "Radar Information Service" or similar.