Cold and flu viruses spread through respiratory droplets and contaminated hands and surfaces. The most effective steps are frequent handwashing with soap and water, covering coughs and sneezes with a tissue or your elbow, and disposing of tissues straight away then washing your hands.
Avoid sharing cups, utensils, towels, and bedding while you are unwell, and regularly clean frequently touched surfaces such as door handles, taps, and phones. Ventilating rooms by opening windows helps reduce indoor virus build-up.
Where possible, keep some distance from household members who are at higher risk, such as infants, older adults, pregnant people, or anyone with a weakened immune system. Staying home while feverish and being most careful in the first few days, when you are most contagious, makes the biggest difference.