亲自(qīn zì) and 亲身(qīn shēn)
"亲自(qīn zì)" is usually used before verbs in Chinese. For example:
亲自去(qīn zì qù), go personally
亲自来(qīn zì lái), come personally
亲自做饭(qīn zì zuò fàn), cook by himself/herself
亲自写信(qīn zì xiě xìn), write letter by himself/herself
"亲身(qīn shēn)" is usually used before abstract verbs. For example:
亲身体会(qīn shēn tǐ huì), to experience in person
亲身感受(qīn shēn gǎn shòu), to feel in person
There are many other such adverbs, including "亲手(qīn shǒu)", "亲眼(qīn yǎn)", "亲耳(qīn ěr)" and "亲口(qīn kǒu)".
"亲手(qīn shǒu)" means making something with your own hands. For example:
亲手做邀请卡(qīn shǒu zuò yāo qǐng kǎ), to make invitation card with his/her own hands
亲手织毛衣(qīn shǒu zhī máo yī), to knit a sweater with his/her own hands
"亲眼(qīn yǎn)" emphasizes seeing something with your own eyes. For example:
我亲眼看见彩虹(wǒ qīn yǎn kàn jiàn cǎi hóng), I see the rainbow with my own eyes.
"亲耳(qīn ěr)" emphasizes hearing something with your own ears. For example:
我亲耳听见他说话(wǒ qīn ěr tīng jiàn tā shuō huà), I heard him speak with my own ears.
"亲口(qīn kǒu)" emphasizes eating or drinking or speaking in person. For example:
我要亲口尝尝北京烤鸭(wǒ yào qīn kǒu cháng cháng běi jīng kǎo yā), I want to taste the Beijing Roast Duck in person.
我会亲口告诉你真相(wǒ huì qīn kǒu gào sù nǐ zhēn xiàng), I will tell you the truth in person.