Here, I only share my personal experience in increasing external links:
1. Through the webmaster tools website, query the website and increase it.
Nowadays, many webmaster tools provide Alexa ranking, Google PR value, and search engine inclusion status queries. After using these webmaster tools, they will record the query status of the website in the database and leave a link to the queried website. There are many such batch query tools, such as Lu SongSong's automated website promotion machine.
To be honest, I rarely use this tool. However, I installed an extension tool in Chrome that can query website information, which might be somewhat useful.
2. Submit web pages to websites like Digg (Juiker)
There are very few Digg-like websites left now, even Digg itself is not doing well. Below, I will share some surviving Chinese Digg-like websites.
Mop Tuike: http://tk.mop.com/
Xiangguo Hotspots: http://xianguo.com/hot (RSS submission required)
QiKe Discovery: http://www.diglog.com/
Waakee News: http://www.waakee.com/
5D News: http://news.5d.cn/
3. Post replies with URLs on forums
WordPress Chinese Forum
Tianya Community: Use the Tianya Assistant Chrome extension tool to modify your personal signature to a URL, but be subtle to avoid getting banned.
4. Write soft articles
Baidu Wenku, Baidu Experience, various blogs, etc.
More...