A short introduction on the general aspects of the language, major dialects and what makes it unique in terms of sound inventory, phonotactics, etc.
Use of the International Phonetic Alphabet is encouraged. (Standard transliteration schemes like SAMPA are OK but not preferred.) Surround phonemic/phonetic symbols with the IPA template, like this:
Even if the IPA symbols are part of the normal Latin script (as in /bid/ "bead", /ki/ "key"), the IPA template should be used to force a consistent style and flag IPA text as such for your browser.
The {{IPA notice}} should be placed on or near the top of the page.
Use the standard orthography for the language where appropriate, but explain how orthography maps to actual phonetics in a different place. This may be on the main language page, or another page called "xxx orthography" (eg Russian orthography). Do not start by explaining phonetics in terms of the written form ("the letter D is pronounced /d/"). Speech came first, and then writing.
All examples of tables and transcriptions here are based on the American English section of the Handbook of the International Phonetic Association ISBN 0-521-63751-1.