What is the referral traffic and how to improve it?
There is mainly four ways to have traffic on his website: direct traffic (world of mouth, known people, etc.), paid ads (Adwords, etc.), SEO and referral traffic. This last one is the traffic you can obtain from other websites, because they put a link to your website.
To increase this number, and have high qualidifed traffic, you will find some ideas here. But keep in mind that to obtain traffic is quite time consuming. But usually the traffic that will result will be high qualified: They already know everything about your niche, or even your website. This is why this should be one of your main long-term goal when working on how to improve the traffic on your website.
Where should I post my link?
Guest blogging
Find the blog relative to your niche, and contact the owner to have a nice article about your website. Usually you will have to pay for this, but links are relevant and the traffic will be qualified.
Blog Comment
Answer blog's article that have a comment section with a good paragraph and a link to your website. People interested in the article could visit your website after reading the article.
Create shareable content
Write easy-to-share articles relative to your niche (TOP 10, List of things, funny pictures). The people will like them and share them on their own website or Twitter/Facebook.
Be active on social media
Be consistent on Facebook/Twitter to show that your brand is active and try to answer every question relative to your industry. Website like Mention.com or Google Alert could be useful for this.
Answer on Q&A websites
Find high ranked questions on your niche posted on website like Quora or Yahoo answers and answer them with a link to your website. Traffic should be really high qualified.
Be active on forums
Be active on community forums, help people and send them when relevant to your website. It could be quite time consuming, but usually the ROI should be awesome!