The way that some of the letters were explained to me, when I first started learning Chinese, was that C = a ts sound, Z = a dz sound, CH = an "inner mouth" ch, Q = a "front of mouth" ch, SH = "inner mouth" sh, X = "front of mouth" sh, ZH = "inner mouth" j, J = "front of mouth" j...
Those are the only "weird" ones, although it's worth nothing that letters like p, b, and d aren't strongly aspirated most of the time.
Then there's the 7 -i syllables (shi, si, zi, zhi, ci, chi, ri) where instead of saying an "ee" sound for the i, you just sort of make the first letters more voiced and extend the sound. The easiest example being that "shi" is almost said like "sure" except without ever quite reaching that R sound.
It's not bad once you get the hang of it, but there are a few tricky things upon first starting, is all! :)
