Public places
Ok, you decided to use public WiFi access point. What can go wrong?
Non-encrypted traffic might be hijacked
Number one rule: don’t use HTTP sites. It is obvious, but it is not comprehensive. The reason is that, in case of third-party applications, it is impossible to be sure that your traffic is always encrypted.
Therefore, let’s proceed to practical advices.
Make sure that WiFi access point is password-protected
Naturally, open WiFi is not protected against sniffing since the traffic is not encrypted. Literally any WiFi device in monitor mode might capture all the traffic.
WiFi access point must be trusted
Use access points only from more or less trusted providers, world-wide networks etc. It is not 100% guarantee of security, therefore, if you are paranoid about security, proceed to the next point.
Use VPN
In public places, only Virtual Private Networks (VPNs) are reasonable solutions. Once you establish VPN connection, all the traffic is encrypted regardless of the fact if WiFi traffic is or not, whether you trust it or not.