There are a couple of points that need to be mentioned here.
This is a 2 fold problem,
1st if a speck of any dust gets on your lens then you have a problem with the calibration of laser power level error message. Compressed air is the way to go to fix this short of taking it in and having it worked on.
2nd there seems to be No Earthly way to impress on users that many of the Media Manufactures produce sub standard Media. Next it is important to note that buying the larger spools seems to be more of a problem than not.
CD's and DVD's are mass produced and the cheaper brands can be a huge issue in some Optical Drive units.
I find that using my drive a lot seems to help.
Using the highest quality media you can buy is also a +
I find that buying Media that is individually wrapped in there own Jewel Cases is also a +
I, like many of you, have suffered from these issues until I did a couple of things to improve my results.
There is such a big difference in the Quality of the Media the first tip is to read the packaging.
Read and you will see that chooseing media that says it will burn at 1X, 2X, 4X, 8X, and 16X will save you a ton of money by not producing what we call Coaster's, or junk.
Using the Quality Media Guide will help as well.
http://www.digitalfaq.com/media/dvdmedia.htm
Using this guide to buying top quality media, I find works for both CD's and DVD's.
Remember that not all Optical Drives are created equal.
Make sure you keep your System UP TO DATE by using the Software Update Feature, this will insure that you have the latest Firmware Updates from Apple.
Next check often with your Optical Drive's Manufacture as well to be sure that you have there latest fixes, and updates.
Following the above suggestions will more often than not solve the majority of problems.
There is much much more, but I won't bore you with the reading that most users won't bother with anyway because they just want everything to work when they put media in there drives.