Where people in English mind their Ps and Qs, speakers of Japanese have to know their o's and go's. These are the little prefixes that attach to all manner of words to make them sound more formal or polite. Known as bikago (美化語, embellishment words), it's a relatively simple trick that works with the ornamental character 御 and its two main readings, o and go.
The textbook rule is that o pairs with indigenous Japanese words, whereas Sino-Japanese words go with go. Examples of the former are o-kome (お米, rice), o-kane (お金, money) and o-sake (お酒, sake). The second group contains words such as go-kazoku (ご家族, family), go-kyōryoku (ご協力, cooperation) and go-shinsetsu ni (ご親切に, friendly).
Unfortunately there are a number of non-indigenous words that take the o reading, too. For example, denwa (電話, telephone), which is normally beautified into o-denwa, not go-denwa. And there are also a few rare cases where just the opposite occurs: go-yukkuri (ごゆっくり, take your time), for instance, where go pairs with a native Japanese word.