CCL:G: g03

My problem is when I use the g03 for the geometry optimization using the command job line:
# opt b3lyp/3-21g**
the results are not much different from the starting structure even when I give a high energy geometry structure, the gaussian does not change it to the lowest energy structure just few changes in the bonds lengths. In other words the Gaussian does not change the geometry to the lowest energy structure, although it gaves me the energy.  why?
And what is the keywords available for getting the lowest energy structure??

can you help me please?