Select the right mirror is very important for you download and update programs on ubuntu.It makes ubuntu download and update in the fastest way.
In fresh ubuntu,the default mirror may not the best for you.Just go to System->Administration->Software Sources
You will see this screen,select Other…at the scroll-down menu.
Click on Select Best Server.After a few seconds of testing download servers,the fastest mirror will be select automatically.
Click Choose Server,then close.A window pops up,click on Reload.