san1 vs tai2 vs san1 tai2
Well, martial arts and Cantonese, you like Bruce Lee? Anyway, here's what you want:

打我心口 - punch (打) my (我) chest (心口)

打我個肚 - punch (打) my (我) abdomen (肚)

打我個頭 -  punch (打) my (我) head (頭)

打我呢度 -  punch (打) my (我) here (呢度) [supposed you pointed to somewhere by your finger, when you say it] 

Sound files:

打　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/daa2.Mp3

我　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/ngo5.Mp3

心口　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/sam1.Mp3 http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/hau2.Mp3

個肚　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/go3.Mp3http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/tou5.Mp3

個頭　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/go3.Mp3http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/tau4.Mp3

呢度　⋯　http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/nei1.Mp3http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/sound/dou6.Mp3

Furthermore, 打 (punch) is assumed using fists. If you need other types of attacks (fingers, palm, elbow, or kick), you need to state clearly to you companions :)

BTW, just curious, which martial arts are you learning?