Choose tank types and site them

Tanks are heavy, long-lived and hard to move. Their position decides water pressure, water quality and freezing risk.

How

Pick an opaque, covered tank with screened vents. The Texas manual says opaque tanks inhibit algae and screened vents discourage mosquitoes.
Use only tanks made for drinking water on the potable line, and never a tank that has held toxic materials (Texas manual).
Site tanks as high as practical to reduce pumping, but below the lowest downspout inlet for rainwater. Every 10.2 m of height gives about 1 bar (the 2.31 ft per psi relation used in pump hydraulics).
Build a stable, level pad. Water weighs about 1 kg per litre; the Texas manual notes a 1,500 US gallon tank weighs about 5,600 kg (12,400 lb). A structural engineer should check raised stands.
Keep tanks out of septic drainfields and, for underground tanks, at least 15 m (50 ft) from animal stables or treated wastewater application (Texas manual).
Shade tanks in hot climates and protect pipes and fittings from frost in cold ones. Leave access for cleaning and desludging.
Keep stored water cool. Legionella bacteria multiply between 20 and 45 °C (HSE), and CDC names 25 to 45 °C as the most favourable range. Shade, bury or insulate tanks in hot climates.

Safety: A full tank stand that fails can kill. Never improvise a stand from untested materials.