The IAU webpage dedicated exclusively to this topic. The following rules apply specifically to the IAU100 NameExoWorlds project:
The proposed names should be of things, people, or places of long-standing cultural, historical, or geographical significance, worthy of being assigned to a celestial object.
Although not necessary, the names may be drawn from themes related to the sky and astronomy, or related in some way to the constellation or a cultural asterism in which the exoplanetary system lies.
In recognition of the UN 2019 International Year of Indigenous Languages (IYIL2019), speakers of Indigenous languages are encouraged to propose names drawn from those languages.
Two (2) names should be proposed - one (1) for the exoplanet and one (1) for the star it orbits.
The two names should follow a common naming theme. The naming theme describing how the names are related in some logical way should be summarized in a sentence or two, and be broad enough that additional names could be drawn from the literature to name additional objects in that exoplanetary system in the future (e.g. additional planets which might be discovered, additional stellar companions). Example: Rivers of country XYZ. Fictional lands in 19th century stories from country XYZ, etc.
See more details below.
1- Proposed names, after translation, should be:
Between 4 and 16 characters in length in Latin alphabet (including spaces or punctuation)
Preferably one word.
Pronounceable (in some language)
Not identical to, or too similar to, an existing name of an astronomical object. Names already assigned to astronomical objects can be checked using these links:
02- In addition, proposed names may not be:
Names of a purely or principally commercial nature.
Names of individuals, places or events principally known for political, military or religious activities.
Names of individuals that died less than a century ago (1919).
Names of living individuals.
Names of organizations related to the selection.
Names of pet animals.
Contrived names (i.e. new, invented).
Names that include numbers or punctuation marks (diacritics are acceptable)
Names that are principally known as trademarks or protected by intellectual property claims.
3- All proposed names should be accompanied by a citation explaining the name of no more than 100 words (after translation into English)
04- The selected public names will be recognized by the IAU as the appropriate publically used name for the object(s)
It is understood that the selected public names will not replace the scientific alphanumeric designations.
The proposed names will be published as such, along with due credit to the proposers that proposed it.
This public name may then be used internationally along with, or instead of, the scientific designation, permanently and without restrictions.