There are no guarantees, but there are some ways to cut your risks.
The most important are avoiding crowds, especially during the peak cold seasons of September, late January, and April; avoiding people who obviously have colds; avoiding shaking hands with people who might have them; avoiding rubbing the nose and eyes; and washing your hands, washing your hands, washing your hands.
These precautions may help because of the way colds are often spread: not just through infected droplets in the air but through particles carried by hand to eye and nose membranes.
The greatest share of colds are caused by rhinoviruses (about a third) and coronaviruses (about 10 percent). Rhinoviruses seem to spread best in droplets from a runny nose, though they may also be sprayed by coughs and sneezes.
Once virus particles land on a surface or someone’s hands, they may remain active for several hours. Then the virus can go from hand to face to eye and nose membranes.
Someone with a cold can be contagious even before signs of illness appear and for a couple of days after it is obvious, so one cannot entirely prevent colds by avoiding people with symptoms, but it helps.
Other useful measures are eating a balanced diet, which is associated with a lower susceptibility, and staying away from children, who get five to eight cold infections a year. Those younger than 2 have the most.