Romain is a great player to learn from who wrote
Hanabi "reference" for bga.
Blacktango wrote in French
Conventions et Techniques.
2 players
These games are mostly based on logic, usually without an agreed set of clue/discard/play interpretations (conventions).
3-5 players
These games are much more interesting, because we can clue a card that is
not yet playable to cause players in between the clue giver and the clue receiver to try to 'fill in the gap' by playing their leftmost,
unmarked card to make the clued card playable.
Applying this technique, we can create increasingly more complex clues and interpretations and this is the basis of BGA Finesse and H-Group conventions.
If you are new to 3-5 player games, I recommend taking a look at the
BGA wiki Examples Prompt, Finesse and Reversed Finesse.
Once you have mastered these moves, Bluff and 'Long' Finesse extend the Finesse concept.
Layered Finesses extend the Finesse concept even further, where there can be other unrelated, but playable cards 'layered' in front of the finessed cards. It is very important to understand bluffs fully to understand when a clue can and cannot be a Layered Finesse.
Words of warning
A large proportion of Hanabi players on BGA are prideful and/or ignorant (myself included, although I try not to be).
Be prepared for rude and condescending players who may try to teach you things without sound logic. If you have thick skin, ask them to explain their logic without using Hanabi vocabulary. Otherwise just ignore them in the knowledge that they only want to feed their pride.
While H-Group conventions are more efficient, some conventions are counter-intuitive and do not follow the basic principle on BGA that we assume clues are the truth (finesse) until they are revealed to be a lie (bluff). But as with most things, best if you try both convention sets and make your own conclusions.