Ack! Alcohol and laser lenses do NOT mix! Sorry guys...but this is very bad advice!
Why?!?! CD-Rom lenses are plastic and have AR (anti-reflective) coatings placed on them. An alcohol and/or methanol solution could remove this AR coating and etch the plastic lens. Once you etch or fog the lens its toast. BETTER to use a photographic type lens cleaner as they are designed not to remove AR coatings. Again this is ONLY if its necessary. Try the methods below first.
Most cleanings only require that you blow short bursts of compressed air across, but never directly into the lens as you could force some grit into the lens mechanism itself.
A CLEAN photographic lens brush can also be used to carefully brush away any offending material. The best type are the ones with a small air bellows so you can blow some air across the lens and then brush. Oh and be careful to not move the lens carrier... you can misalign it if you are not careful!
Before you post, "but my CD-type cleaner has a brush attached to it..." Have you noticed how fast a CD spins in your drive? Your brush will SCRUB rather than brush across your lens at a very high rate of speed. If your lens has some serious grit....SCRATCH!!! That is why they are potentially dangerous.
Lastly, be careful about opening the CD-Rom case during the warranty period. Most manufactures will void your warrantee if you open it up. If the drive gives you CD read problems during the warrantee period, have it cleaned by an authorized dealer.