Never drink tap water.
Bottled water is generally safe – check the seal is intact at purchase.
Avoid ice.
Avoid fresh juices – they may have been watered down.
Boiling water is the most efficient method of purifying it.
The best chemical purifier is iodine. It should not be used by pregnant women or those with thyroid problems.
Water filters should also filter out viruses. Ensure your filter has a chemical barrier such as iodine and a pore size of less than 4 microns.