Make sure that the bevel is facing upwards so you will not blow the vein when advancing forward.You can control the angle of insertion more when the bevel is facing upwards. You will also have easier glided point of entry as the sharp end-tip of the needle enters the skin.  (Source: http://www.nursebuff.com/2014/10/tips-for-nurses-on-how-to-prevent-blown-veins/)