It really depends on which ad scheme you are running on HubPages.
If you are on the HP Adprogram then the only Google Adsense ad you get directly paid for clicks is the one at the bottom of the page on the right. You can try and optimize this by how you display your comments etc, but it's really not going to improve much. Many people will never click on it as it's so far down the page. If you somehow manage to get a click through rate of higher than 0.05% please let me know how you managed it!
If you are solely being paid through Adsense on HP then you're best bet would be to optimize the position of the in-content ad. Traditionally, the higher up an ad is on the page the more likely it is to be clicked. However, now you have to balance this with the Google update that penalized sites that were too heavy with ads above the fold. You can experiment and see the best place on the page.
That being said, I would focus more on how many articles you write, what you write about and getting ranked in the search engines. If you concentrate on these 3 aspects the clicks will take care of themselves.
Best of luck!