If you are seeing a spot, it probably is dust on your sensor, not on your lens. - Robert Scoble

In which case, one should consult a camera shop if you're not willing to clean the sensor yourself. - J.T Dabbagian

usually manual explains how to cllean sensor - you'll need one tool for sure, rubber pear-shaped pump ;) - A.T.

If it is an SLR, it could be dust on the back part of the lens. If the spots aren't in the photos but you see them in the viewfinder, check the back of your viewfinder, the focus screen (only on higher end cameras), and the mirror. And if it is dust on the sensor, you could try these: http://www.visibledust.com/product... - Patrick Binder

most def a spot on your sensor. dare to clean it yourself or bring it to a shop. I recommend the latter. - Don Martelli from twhirl

doing it yourself is ok, don't get me wrong, you just need the right "stuff." Here's a video on the "how." Disregard the promo stuff about the product: http://www.youtube.com/watch... - Don Martelli from twhirl

Sensor dust. I use one of these: http://www.giottos.com/Rocket-... safe to do by yourself (I've only needed to do it like twice in the last year; only use it if you can see the spots noticeably). Shoot a white wall at something like f/22 to find the spots. - Benjamin Golub

I have and use this product - http://cgi.ebay.ca/CleanSk... . Some spots though require a liquid based cleaning procedure. You can buy diy kits for that as well but I take mine to a pro. - Brian Sullivan