On the optical instruments in my lab I use absolute Ethanol, careful
not to touch plastic or rubber components, using COTTON balls to clean
the lens. After the ethanol we generally just blow on the lens, clean
off again with cotton ball. Sometimes there is a little cotton residue
left that just blows off with a hand blower. Now with camera lenses I
have to admit I am a little more cavalier. If they are real bad I'll
dust them off with a fine brush, then determine if they need the
alcohol treatment or just a clean (sometimes not so) COTTON Tshirt. I
don't clean my camera lenses often, you can have a nasty looking lens
and not have much effect, on the image. That said of course the best
images come from a clean lens. I try to keep a lens cap on my lenses at
all times, this minimizes dust, inadvertant finger touching etc.
So my advise is, keep your leses capped, when not in use, and don't
apply any undue pressure when cleaning, use COTTON balls, or surgical
cotton, Kodak makes about the only lens paper I'd use, most other
brands are too stiff. When using lens paper don't use a single piece,
take about a quarter pack and roll like a cigarette use the end of the
roll to clean. Try to keep the lens as clean as possible without
cleaning. Obsessive cleaning leads to scratches.

Tom

I use lens cleaning solution on microfiber cloth. After the lens is
dry, I use lenspen.

http://digitcamera.tripod.com/#slr

If the haze is internal then you should refer the lens to a shop for an
estimate.

To remove any surface 'film' I use Kodak Lens cleaner and Kodak tissues.
 Vary sparing amounts of liquid are all that are needed.  I do this
less than once/year per lens and only when needed.

For dust and whatnot I use a "camel" hair brush to remove the dust and
then microfiber cloth if needed for whatever else may get there
(fingerprints for instance).

I've _never_ cleaned a rear element of one of my lenses beyond blowing
off a spec of dust.  I do make absolutely sure that the rear element is
either in the camera or capped.

Don't be excessively worried about coatings, they are quite hard.  With
common sense care your lenses can be blemish free for a lifetime.  And
if a lens front element does get a scratch you can have the scratch
filled with black ink: won't change the image at all and will prevent
flare artifacts.

Finally, whenever working where there is a lot of blowing (sand, dust,
rain, mist, salt, grit, ...) then use a filter as an additional
protection and shelter the gear when changing lenses.

Cheers,
Alan.

I usually breath on the glass and use my cotton t-shirt.  But then, all of
my lenses have filters on them so the only thing that ever gets dirty is the
filter.  There's no reason why the rear element should get dirty.  And, when
all else fails I use Kodak lens fluid and lens tissue.  Works as good as
anything out there.  About the only way you're gonna scratch the lens is if
you get some dirt trapped in the tissue or lens cleaning cloth.

Use lab grade Isopropyl Alcohol, a microfiber cloth moistened with it.

DO NOT RUB IN A CIRCULAR MOTION.  If there is any abrasive in the
cloth a circular motion will create many circular scratches on the
coating.  Use a straight cleaning motion, doing one stroke and then
check the lens.

You should also first blow the lens clean with a hand blower but for
any thing touching the coating.

What about using the sensor cleaning solvent?
Eclipse = methanol

http://www.lenspen.com/409

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