warts are contagious...caused by a virus.

They usually occur where there is reduced blood flow...because the immune system cannot get to them easily to remove them.
If your immune system is not up to snuff, warts may be easy to contract.

I do some Googling about how to avoid them and keep them from spreading.

People walking barefoot alot, are at risk for plantar's warts.
If you shower in a gym wear flip flops and rinse them periodically in a dilute bleach solution. If you wear sandals without socks, rinse the liner with alcohol periodically. This applies to new sandals, as they may have been tried on by someone who carries the wart virus.

This link is quite good and may be helpful for you:
Plantar Warts & Verrucae :: Diagnosis & Treatment Information