I keep all of my hubs if I believe that they are good quality and like Neinahpets says, I edit them and add new content in an effort to make it more interesting and relevent. I also work on making them more search friendly so they'll come up on google and other search engines. To get more traffic on hubpages make sure that your hub is properly categorized and has a descriptive title ad summary that are user friendly!
I also backlink/cross-promote my hubs by including a description and link to them on my other hubs and I colloborate with other hubbers by providing links to each others related hubs on our own. To do this make sure you message the hubber first and ask them if it's okay. I've learned that it's bad etiquette to be posting actual URL's for your hubs when commenting on other people's hubs. So I just put in the title of my hub instead and ask them to check it out if it's similar to what the wrote about.
Another way to generate traffic on hubpages.com is to find other hubs that are on similar/same topics as yours and comment on them to start a discussion and encourage people to check out your relevent hub(s)!
What also really helps me is posting links to your hubs on social media sites like facebook, but only if they are relevent to your friends/followers! I also joined a bunch of special interest groups on facebook that I like and are relevent to what I write about. In addition I created a fan page for my hub profile and this way I can get people outside of my friend's list/personal profile to read my hubs!
For example I write a lot of articles about salsa and latin dancing, so I post my hubs on the pages of a lot of salsa groups that I am a member of on facebook. It's also good to create special interest list of your facebook friends so this way you can post something on your personal profile that will only be visible to that list and you avoid spamming your other friends who aren't interested.