More the number, less the seriousness of the leader
Countries like San Marino, Andorra and the Vatican. They are recognized by most nations, have governments, mostly part of the UN but are not commonly known. (Other than the Vatican). Famous examples include: Malta, Liechtenstein, St Kitts and Nevis, Tuvalu, these generally aren't considered and shouldn't be counted as micronations and are mostly called microstates. These nations are what most non micronationalists class as 'Micronations' or 'MicroStates' This was certainly the case during the time when nations like Molassia and the Aerican Empire were relatively small.
Separatist MovementsCountries fighting independence with several people on their side. These are cases like Somaliland, Catalonia and Kurdistan. They have their own language and are significantly different to the country they are owned by. They have a large chance of becoming independent. Also shouldn't be considered as a micronation.
Countries that could be independent and have some sort of difference to their country however don't have such a big crave for independence. These are countries like Zanzibar or Jersey.
Countries like Molossia, Liberland and Sealand. These are serious countries that the owners make a living over Passports, Media and their nation. These nations are widely known by the general public unlike San Marino or Andorra. It is almost impossible for these nations to become independent but are known by the government of their country. These Micronations often have Wikipedia pages.
Countries where Micronationalism is a big hobby and they take it seriously. These nations' leaders have suits, turn up to conventions and have flag poles. These nations are normally on the MicroWiki community. Key examples are: Adamia, Austenasia the Aerican Empire, Terrexa, Luxia, Vlasynia, Egan, and the Titanist Union. These nations have mediocre publicity from die hard viewers of Vice and WatchMojo.
Effective Control Micronations
Countries like Arbor Lignum that have a small portion of land that they fully own. These are countries that mostly own farmlands and hamlets. These nations have a lot more control than the typical micronation however are still quite small.
Countries like Alanland and Alimia claim land in their houses or flats and are part of communities and have no intention of becoming independent and only treat micronationalism as a small hobby. These are just normal people with normal jobs but have their own nation. You may think this is the least formal tear but there are still more.
Countries that claim a large portion of land, but only few people claim citizenship. For example (no disrespect for these nations) The Princian Empire claims a big portion of the UK but only few people know about it Princian citizenship. These nations have capitals with millions of people but little to none of those people know or care about the nation in question.
These nations are often referred to as anti states. This means they claim land in Antarctica, the Moon and small rocks. This is mostly a political statement. Republic of Davelandia is one of these examples
Kids who claim their garden as a country and do roleplay. We've all got to start somewhere, like the early stages of Empire of Valdenya!