My mothertongue teacher suggested the following "Pinyin false friends list". She spoke about the "7+3+5" false friends:
- The 7 are
z c s zh ch sh r, after which
i is pronounced, she said, as "silence"; this, as I said in a comment, equates to either always /ɨ/ or, more accurately, a trailing syllabic voiced fricative, i.e.
zi ci si zhi chi shi ri =
/tsz̩ tsʰz̩ sz̩ tʂʐ̩ tʂʰʐ̩ ʂʐ̩ ɻʐ̩/, or one may say
/ʐʐ̩/, that varies from speaker to speaker;
- The 3 are
j q x, after which
u is pronounced like
ü in any case; that is because
j q x are alveolo-palatal, and are thus never used before non-palatal sounds like u; that also explains why
z c s zh ch sh r have the above sounds with
-i: i is palatal, they are not; in fact, what used to be
*/tsi/ etc. "collapsed" into modern
ji etc., and so did
*gi etc, according to Wikipedia; this is why
Beijing: it used to be
*Beiging and got Wade-Giles
Pei-king, and lost the
i for "English phonetic representation";
- The 5 are
ui iu ian üan o, which are pronounced as
uei iou ien üen we respectively.
Now I do not agree to the
o. Or rather, it needs specifications.
o by itself is, AFAIK, only present in the 4 characters
哦喔噢嚄, which are interjections and exclamative particles, and which I would pronounce
/o/ – I'm not a native though, so this must be taken cum grano salis, and they are sometimes rendered as
o is a syllable final (e.g.
bo po mo fo, actually those are the only examples, as elsewhere you find
uo) it is usually pronounced
/wo/. Wikipedia has this table and note three in this one agreeing with this view. Also, this Wiktionary entry, for example, translates
/-u̯o/, which is essentially
/-wo/. With this, I think the 7+3+5 rule is a good mnemonic for these spelling-sound discrepancies.
See also here for further reading and comparisons with other Romanizations such as Wade-Giles.
There is also another thing: tone sandhi (Chinese
连续变调). Basically, third tones often change. Base rule: 3+3 -> 2+3, i.e. nǐhǎo is pronounced níhǎo. For sequences, see here and linked questions. There are also tone variations of
不, which are sometimes marked, but often not marked. For those, if you are not satisfied with this, I suggest you ask another question.