This could turn into an extremely long post if we go into everything in detail here 
A good site structure should be one that is hierarchical and sensible. By this, I mean it should make sense when someone lands on a page, what your intentions are for them and how to achieve them. Keep your call-to-actions clear and concise and don't burden the page with wasted content.
Your URLS's should again be descriptive, so that if someone were to land on an internal page, would the URL tell them a bit about where they were? Are the key phrases you are targeting included in the URL itself? Also, you should aim to keep your URL structure to within 3-4 click of the homepage. Any more and it turns into a poor user experience.
Your meta titles and descriptions should also be in target for the pages themselves. Something like this:
<pin code:="" lohit,="" arunachal="" pradesh,="" india,="" <your="" site="" name="">or <pin codes="" for="" lohit,="" arunachal="" pradesh,="" india="">Whatever you decide to go for here, I would keep i to under 60-70 characters, with the most important information towards the start.</pin></pin>
I hope that helps a little.
-Andy