_The Oxford Advanced Learner's Dictionary_ is an excellent place to become familiar with the International Phonetic Alphabet (IPA). You can enter just about any word and it will give you the IPA transcriptions for it and also audio pronunciations of the word in British and American English.
There is a one-to-one correspondence between an IPA symbol and its ASCII IPA symbol. The correspondences are shown in a FAQ file at
http://www.alt-usage-english.org/ipa/ascii_ipa_combined.shtml / "The symbols"
The dictionary is online at
http://oald8.oxfordlearnersdictionaries.com/dictionary/ .