I have been studying for this VMware VCAP5-DCA exam for the last 2 months. This exam is for vSphere 5.5.
One of the best study guides is to watch Jason Nash's VMware vSphere Optimize & Scale
Then I read the VCAP5-DCA Official Cert Guide:
The last one is to do the VMware Hands On Lab which is the best for you to use it for lab and try some of practice concepts.