Add 1/10 volume of 3 M Na-Acetate pH 5.2, and 2 to 2.5 volumes of ice-cold 100% ethanol to the DNA sample
Mix, and store at -20°C for at least 1 hour to precipitate the DNA
Recover the precipitated DNA by centrifugation at full speed in a microcentrifuge for 15-20 minutes
Pour off the ethanol and wash the pellet twice with room-temperature 70% ethanol
Allow the DNA pellet to air-dry
resuspend the DNA in a suitable volume of sterile TE buffer or distilled water