Recording

The only way to be certain that nobody is listening in on whatever your saying, is by making it impossible. With some headsets, you can directly remove the microphone. With ones that have two cables, you can unplug the microphone one. This method however doesn't work with phones' and laptops' built in microphones as they're too much of a hassle to disable and re-enable.

Luckily, cameras (on devices you own) are a much easier issue to solve. Their placements are obvious and can always be covered up if wanted.

[Never ever connecting to a network or internet source is also an option]