It's called palatalization.
The letter "t" is pronounced as an affricate, [ch], before a high vowel:
fu
ture
sta
tue
congra
tulations
(Note, /t/ is often voiced to [dj], as in
jump: congra[dj]ulations
Also, the letter "t" is pronouced [ch] before "i" and "e":
righ
teous (Note, phonetically "e" is [I])
Chris
tian
ques
tion
Notice also the sounds that come before "t". In our three examples above, fricatives "gh" and "s" come before "t". Look at words where "t" is preceded by a stop, or plosive,
cap
tion
atten
tion
/t/ is pronoucned [sh].
Look for words that have medial "ti" and "te", preceded by fricatives. That's a start.