根據
http://idioms.thefreedictionary.com/
make it up as one goes along的意思是
To improvise continuously as one does something; to do something without formal guidelines, structure, rules, etc.
即類似見機行事, 隨機應變的意思
None of us really knew how to play the game, so we just made it up as we went along.
我們當中沒有人知道要怎麼玩這個遊戲,所以只好隨機應變。
I completely forgot the rest of my speech halfway through, so I just started making the rest up as I went along.
演講到一半,我完全忘了剩下來的演詞,所以我只好臨場發揮編詞。