Being prepared for unpredictable conditions will allow you to travel safely every day. Make sure that you bring enough water to stay hydrated in all seasons. The clothing you ride in should protect you from seasonal conditions, and should enable a full range of motion. Pack a rain coat and gloves to protect you from rain and wind. Wear clothes that would be slightly too cold if you were walking, you will warm up as you ride. Winter, spring, summer and fall riding clothes are all different, and layering the right things for the right season is essential.
Preparing your bike is a two-fold process. You already read about keeping your bike happy mechanically. This is an excellent way to prevent unpleasant surprises on your commute, but one must also expect the unexpected. We recommend carrying a patch kit or a spare tube, some tire levers and a small pump with you so that you will not be left stranded if your tube should pop.