Wild camping is the best part of riding far, and the part with the most unwritten rules. Here is how it works in practice: which countries are relaxed, which are not, how to choose a place you can leave without a trace, and where to find spots other riders already tried.
There is no single European rule. Some countries have a public right of access that lets you pitch a tent away from houses for a night or two. Others prohibit camping outside a campsite, and enforcement ranges from strict to never seen.
As a rough orientation, not legal advice: the Nordic countries (Sweden, Norway, Finland) and large parts of Scotland are built around public access rights. Much of Central and Southern Europe, including Germany, France and Croatia, restricts or prohibits wild camping, often with exceptions for one night of emergency rest or for particular regions. In the Balkans the written rules are often strict while remote camping is tolerated in practice.
Rules also differ inside a country: national parks, nature reserves, beaches, forests in fire season and private land are the usual exceptions. Check the official tourism or park authority for the region you ride through before you go, and ask locals when you can. Rules change.
A loaded bike is easy to spot and easy to steal. Park it where you can see it from the tent, lock the steering, and use a disc lock or a chain when the place is not remote. Keep valuables in the tent, not in the panniers.
Ride the last stretch to a spot in daylight if you can: an unknown track is much harder in the dark, and turning a loaded bike around on a slope is the classic way to end the day with a dropped bike.
Two Wheels Apart is a free iOS map built for exactly this. Riders mark wild camps, campsites, water and workshops with photos and a description, and a spot can be verified by the person who shared it. You see distance and the fastest route from where you are, and you can leave your own spots for the next rider.
Sharing your position is off until you switch it on, and even then other riders only see it displaced by about one kilometre, so you can be findable without being trackable.
It depends on the country and often on the region. Sweden, Norway, Finland and much of Scotland allow it under public access rights. Many other countries restrict or prohibit it. Always check the official rules for where you are riding.
Often not. Beaches, dunes, nature reserves and national parks are among the most commonly protected places. Look for signs and check local rules.
Look for spots shared by other riders with photos and a description, check the ground and the surroundings on arrival, and trust your feeling: if a place feels wrong, ride on.