Before I ever wipe the front or back of a lens, I always use a Rocket Blower and give it a few good puffs of air to dislodge anything that might be on the glass itself.
You can find these are most camera stores for under $10 and they are small enough to fit in any camera bag. No matter which bag I'm carrying, I always throw in my Rocket Blowe and my LensPen. I try to never use compressed air as I've heard the horror stories of the liquid coming out on a lens and ruining it when it freezes it.
Once I blow the glass off, I carry a little soft lens cloth around in the bag also, and I wipe any fingerprints or smudges off with that. If there is a real stubborn smudge on there, I have some liquid lens solution on there, but never spary it right on the lens itself. Always on the tissue, then wipe it on the glass.