Along with preventative washing of your hands, I'd suggest expanding that to face washing, too

[Siwsan]

Seriously - just a good reinforcement because so often face touching is such a subconscious activity. Follow it up with some nice moisturiser, and it can only help. Also read that keeping your hands moisturised, to counter the drying results of so much hand washing, is pivotal because dry skin is more susceptive to absorbing.

[morillon]

1. Tooth brushing is good in general

Several years ago, I had to have a pleurectomy due to a bad reaction to a chemo drug, and I spent a week on the thoracic/cardio/pulmonary ward at a local hospital. One thing they had all of us doing was brushing our teeth 3+ times a day, along with mouthwash. They'd found -- and these results have been repeated elsewhere and published in the literature -- that very good mouth hygiene reduced in-hospital pneumonia by 80%.

Anything you can do to reduce the germs and other crud making their way out of your mouth and into your throat (and possibly into your lungs) is a good thing, and when I have even the hint of a cold, I step it up.

[Siwsan]

2. Add some hydrogen peroxide to the gargling/rinsing routine

I can't see how it would hurt.