to come = lái or 来. (note the rising tone on the a) / english word with phonetic approximation = lie to go = qù or 去 (note the falling tone of the u - also the "q" is pronounced like "sh") / english word with phonetic approximation = shoe to buy = gòumăi or 购买 (note the falling tone on o and falling then rising tone on the a) / english words with phonetic approximation = go my to want = xiǎng 想 (note the falling then rising tone on the a - and the "x" sounds a bit like "sh" but with a slight whistle, like the french would pronounce it and the "g" is soft, almost not even heard) / english words with phonetic approximation = she on I want to drink beer = Wǒ xiǎng hē píjiǔ. / english words with phonetic approximation = Woe she on huh pea-chya-oh. Now, I write this, not because I am fluent in Chinese, but rather, to demonstrate that infinitives like these are easily handled by http://translate.google.com/. Sometimes, you should start there.