I signed up here to write, share and learn. When I learned that you can make money, it was a welcomed plus. I'm new to monetizing through writing so bare with me.
Using keywords in your articles is a good way to drive traffic to your hubs. Check Google adwords for keywords that you can use. Keywords are used by people as search strings. Use them so that search engines can easily identify your article and suggest it to those who are looking for information. But be wary not to over do it. Never sacrifice the quality of your hub just to insert keywords.
Links are also important to direct traffic to your hubs. You can share links with friends, social networks, other website, and other hubs. The more people who knows your articles and visits them the better.
Good writing is a must. From content to grammar, every detail must be exceptional. People want to read, learn and get information. If it's not a good read people will not recommend it or even take time to finish it.
Hubpages is partners with e-Bay, Amazon etc. Check the Earnings page under your My Account link for more details. What's great is that these programs can be customized to show products relevant to your article. You can add capsules to your articles and customize them there.
Write great articles that people want to read, drive traffic to your articles and you can earn. I'm not really sure how accurate this answer is but I guess this is a start. I'm sure other hubbers will come along and fill you in on how to earn more.
If you love writing you'll love it here. You can earn from doing what you love.