The Tao of Transistor Biasing
The basic principle is easy to describe:


An npn transistor in common-emitter configuration needs a forward-biased B-E pn junction and a reverse-biased B-C pn junction.
For realizing these requirements with one single supply voltage it is common practice to use a positive voltage (at least several volts)  between collector and common ground (VCE) and a resistive voltage divider producing the required B-E voltage of app. VBE=0.7 V. 
More than that, it is highly recommended not to ground the emitter but to use an emitter resistance RE (app. 10%...20% of the collector resistance RC). This resistor provides negative DC feedback and stabilizes the bias point against tolerances and temperature influences.