which is the best arrangement for a bjt amplifier​

 

by "arrangement" do you mean common emitter vs common base vs common collector? All of these setups have different properties of input impedance, output impedance, and gain. None of them are "best" for all applications, because different applications have different requirements and constraints.

Improving an amplifier often involves using multiple BJT's to get the better gain, frequency response, and impedances as needed.

*edit* I suppose I should include sources:
http://en.wikipedia.org/wiki/Common_emitter
http://en.wikipedia.org/wiki/Common_base
http://en.wikipedia.org/wiki/Common_collector
The AAC section on BJT's is also good for comparing amplifiers
http://www.allaboutcircuits.com/vol_3/chpt_4/index.html