Increase the primers length if possible and redesign the primers again with optimum requirements. 

Redesign your primers and run a PCR in silico to check they do not dimerise. I use  a freeware program called serial cloner.

http://serialbasics.free.fr/Serial_Cloner.htm

Other than that optomise your annealing temperatures by performing a gradient PCR.

Hi Digvijay

I usually do three things to reduce sec. structures:

-Temperature gradient for T optimization;

-Reducing the primer concentration;

-Adding a time increment can also help. In addition,  you can also try to adjust your MgCL2 concentration to increase the specificity of your reaction.

Good luck, I hope some of this helps,

D

1: Reduce primer concentration, and optimize by Temp gradient reaction (see Dusan)

2: Design a new set of primers with better algorithms that address dimer issues.

3: Search if someone else has published a primer set that has worked fine earlier for your target template. 

I concur with previous answers. If problems persist following optimizations you could additionally try touchdown PCR. I assume you have already tried HotStart PCR.