Do not clean your lens (too much). Cleaning marks are by far the most common source of damage to lenses. Shooting under normal conditions, it takes a large amount of dust and grime to have any effect. The same approach applies to filters; good filters use the same type of glass and coatings as your lens (though perhaps not the same absolute quality).
This is the approach I try to take with my various old lenses (some dating from the 50s):
How to clean less
- Use a hood. This will protect the lens from accidental finger-marks, light rain and other hazards when you're actually using it.
- Put the cap on when you're not using it.
- Put it in a case/bag/drawer when it's not on the camera (remember to use a desiccant if you live in a humid part of the world and will be storing it for a while).
- Store it lying down. Dust drifts downwards, so don't point the front/back element upwards.
Alternately or additionally to the above, a protective filter. I wouldn't personally recommend it, but many people (particularly camera store sales staff) do, so it may be an option for you.
How to clean best
Materials: I use a camel-hair brush from the local art store. I just picked the softest one. A good camera store will stock similar, or something like a LensPen. For cleaning solution, I use ROR, which is a mixture of dilute ammonia, isopropyl alcohol, and a mild surfactant. Microfibre cloths are pretty easy to get these days, but the oldest cotton t-shirt you own is also a decent choice, particularly if you haven't washed your microfibre cloth recently.
- Brush/blow away big dust.
- Consider stopping there, it's probably 90% of the problem.
- Spray a small amount of ROR on the cloth. It should not be wet, too much will streak.
- Wipe gently, try to use a new section of the cloth for each stroke.
- Do not rub or scrub, just repeated gentle wipes.
This can take 20 minutes for a lens that's sat in the closet of a heavy smoker for 15 years, but for a lens in daily use is perhaps a 5-minute job, tops. For a bit of context, most of my lenses have been cleaned like this once, when I bought them. Thereafter, just a brushing now and then, and another cleaning only if I manage to stick my thumb on them (or similar).
Credit where credit is due: this is a fairly common approach, but I first saw it in Karen Nakamura's section on Cleaning and Maintaining Classic Cameras which is a great source of information.