The following guidelines for phonetically converting proper nouns into Toki Pona-style forms was written some years ago by Toki Pona's creator, Sonja Lang.
It is always better to translate the "idea" of a foreign word before attempting to create a new phonetic transcription that may not be recognizable by everyone. (Example: Jean Chrétien, Prime Minister of Canada, becomes jan lawa pi ma Kanata, rather than jan Kesijen)
Use the native pronunciation as a basis, rather than the spelling.
If more than one language is spoken locally, use the dominant one.
If it does not belong to any one language, use an international form. (Example: Atlantik becomes Alansi)
Use the colloquial pronunciation that locals actually and commonly use, rather than the "proper" or standard pronunciation. (Example: Toronto becomes Towano, not Tolonto)
If a person chooses tohave a Toki Pona name, he can choose whatever he wants and does not necessarily have to follow these guidelines.
Names of nations, languages, religions have already been established. If one is missing from the official list, make a suggestion on the Toki Pona discussion list.
If possible, find a common root between the name of the nation, the language and the people. (Example: England, English, and English(wo)man provide Inli.)
Cities and locations can be given a Toki Pona name, but they will only have an official name if they are internationally known.
If full Tokiponization would compromise intelligibility, you can always leave a foreign name as is.
Voiced plosives become voiceless. (Example: b > p, d > t, g > k)
[v] becomes w.
[f] becomes p.
The trilled or tapped [r] of most world languages becomes l.
The approximant r of languages like English becomes w.
Any uvular or velar consonant becomes k, including the French or German r.
At the end of a word, The sh sound may be converted to si. (Example: Lush > Lusi)
The schwa can become any vowel in Toki Pona and is often influenced by neighboring vowels for cute reduplication.
It is better to keep the same number of syllables and drop a consonant than add a new vowel. (Example: Chuck becomes Sa, not Saku)
When dealing with consonant clusters, the dominant plosive is generally kept, dropping fricatives such as [s] and laterals such as [l] first (Example: Esperanto becomes Epelanto). You may also choose to keep the consonant at the head of the new syllable (Example: Atling becomes Alin).
Approximants like [j] and [w] in consonant clusters can either be converted into a syllable of their own (Swe becomes Suwe; Pju becomes Piju) or dropped entirely (Swe becomes Se; Pju becomes Pu).
In some cases, it is better to change the letter order slightly, rather than dropping a sound. (Ex: Lubnan becomes Lunpan, not Lupan or Lunan)
Dental fricatives such as English th can either convert to t or s.
The illegal syllables ti, wo and wu convert to si, o and u. (Example: Antarctica becomes Antasika)
Affricates generally convert to fricatives. (Example: John becomes San, not Tan)
Any nasal consonant at the end of a syllable converts to n. (Example: Fam becomes Pan)
Nasal vowels (in French and Portuguese) also convert to syllable-final n.
If necessary to preserve proper syllable structure, the consonant w or j can be inserted as a euphonic glide. (Example: Tai bccomes Tawi; Nihon becomes Nijon; Eom becomes Ejon). It may also be possible to relocate a consonant that would have otherwise been dropped in the conversion. (Example: Monkeal becomes Monkela, not Monkeja; Euska becomes Esuka)
Voiceless lateral consonants convert to s.
If necessary, you may want to tweak a word to avoid a potentially misleading homonym. (Example: Allah becomes jan sewi Ila, not jan sewi Ala—no God). If possible, use a related word in the source language rather than introducing an arbitrary change. (In Arabic, Allah actually means the God, whereas Illah means God.)