Hi Vinay, You can earn credits for your contribution to Tripoto, you can publish your articles on Tripoto and answer questions on the community forum. You can avail your earned credits on your next travels.
For each content contribution you get up to 100 points, and the points are usually credited to your profile. Every month we have a leaderboard contest, three contributors with the highest contributions/credits win free trips! For each answer on the forum you can earn 3 to 25 credits, as and when the answers are upvoted/wishlisted. Visit this link for more info contests that let you travel for free!
https://www.tripoto.com/travel-for-free-contest
Spread the word. Write blogs, create videos and spread them through various social networking channels and websites and get followers. You can also get sponsors once you have good number of followers.