Answer:
There are several ways to spell words phonetically. The easiest way is to write out the word in terms of other words or syllables that people will understand how to pronounce. This is called pronunciation spelling. For example, "pseudonym" could be written as "sue-duh-nem." However, this can cause problems as different people may interpret it different ways. Also, it's hard to indicate emphasis, unless you perhaps capitalize the stressed syllable. If you want to write down transliterations of words in a foreign language class that only you are gong to be looking at, this method can work, but it can also cause a lot of confusion.
The second way is to use the pronunciation guide that you would find in a dictionary. Normally they will have an index or chart with a list of how all the phonemes are pronounced when they write out their pronunciations. However, these can vary from dictionary to dictionary and are often heavily dependent on diacritical marks, so it's not always useful.
The third method is the International Phonetic Alphabet (IPA). This is a system of writing out words based on a phonemic alphabet, using one letter for each phoneme (unit of sound). This way, you are able to transcribe any language in the world with the same alphabet. The entire International Phonetic Alphabet is huge and somewhat difficult to learn, but for English alone it isn't too hard to master. Many of the phonemes are more or less the same as our letters. IPA is used primarily by linguists and language students, but it's helpful for others as well.
In conclusion, for most things all you would have to do is pronunciation spelling. However, the most accurate method is the International Phonetic Alphabet, but it is somewhat specialized.
TO SUMMARIZE, best method is usually the SIMPLEST : pronunciation spelling using very Basic English as much as possible ( rhyming is helpful ), together with capitalized stress.
For example, nuclear : new - CLEAR , also new - kuh - LEAR in ex-President Bush's Texas.
Remember that Dictionary Pronunciation is more precise than Conversational English Pronunciation on the streets in many regions of North America.