This is one of the most frequent characters in modern Chinese. Earlier it meant 'this' and it's interesting to speculate on the meaning change it went through to get to 'be'. The phoneticians tells us it is usually tone neutral in everyday speech, but native speakers working on Bridge to China have frequently disagreed with this.
The hand radical on the side helps us here, but shì isn't much guide to the pronunciation!
Common word: 提供 tígōng 'provide, offer'
Common word: 问题 wèntí 'question, problem'