You have to see the legal
requirements two ways:
1) towards the boat,
2) towards the crew.
The boat needs a registration
The crew need passports.
Now, depending on where you go, you may need the visa or not. Now, depending on where you go, you may have to pre-advise the local authorities, or not. Same rule
applies to insurance
In most cases, you enter the country, contact the marina master or harbour master and they tell you where to go first, then the officials will sort of push you along.
You may be able to know most (but at times not all) the info by:
- reading the countries´relevant websites,
- reading recent cruising guides
- reading info on e.g. noonsite, (under ´formalities´),
- searching/asking on the Cruising Forum, other forums
- talking to other sailors going the same way.