After penguin update, what kind of link sharing technique can help? Where can we exchange niche related links ? Thanks in advance.
If you have to classify it as a "link exchange" you're probably heading down the wrong road. Google flat out bans link exchanges in the Webmaster Guidelines so I wouldn't mess around with them. What you can do instead is focus on building actual partnerships. For instance, say you own a pet store---what kind of similar but not directly competing businesses could you partner with? Maybe a local dog walker, a organic pet food company, or a Golden Retriever breeder? You not only get a link on their site, but you develop a fully blown partnership that includes cross-promotion, writing for each others' blogs, getting incorporated into their company newsletter and so forth. Look for links that are going to be worth more than just a link down the road.
Link exchanges don't have much effect like before, even if you do link exchanges with a site that is on the same niche. If the site owner is willing, then you can guest post on his site with a link back to yours, and you can refer to his site as a reference on one of your articles. This kind of "link exchange" looks more natural to search engines. Hope that helps. Have a good day!
As for post-Penguin link sharing, remember that your links should appear as natural to Google in the first place. And of course try to optimize your backlink profile, check links, do revision on a regular basis, get links via social media and social bookmarking sites, combine 'dofollow' and 'nofollow' backlinks. While targeting high PR sites for backlink oportunities, you may also get a few backlinks from sites with lower PR than yours for diversifying your backlink profile. As for link exchange, it does not work any more in that 'old school' sense. Instead of reciprocal link exchange, go for article submission to web 2.0 sites, guest blogging and forum commenting. This way, if you stay relevant and keep sharing interesting and informative content, - you have better chances to increase SERP visibility and improve your rankings without risk of being penalized.
I agree with what has been said partly. Reciprocal links can be harmful if you over do it. If you are looking to get a load of links this way, which is a great cheap method. Buy a few domains with PR, and throw a little content on the site. Next, look for link exchange offers, but explain to the person looking to exchange the links that it will be better for them if your link comes from another high PR site (the domain you have just bought for $20) Link their link to your money site, or a feeder in which you are looking to increase the PR and give them a link back from the domains you have bought specifically to do this.