This piece for Malachain collects the advice that holds up in practice.
Old phones, laptops and chargers contain valuable metals as well as substances that should not end up in household waste. Most areas offer collection points at recycling centres or electronics shops, and many manufacturers run take-back schemes. A device that still works may be more useful donated to a school, charity or community group than broken down for parts.
Before handing anything over, protect your data. Back up what you need, sign out of accounts, remove the device from any find-my-device service and perform a full factory reset. Take out memory cards and SIM cards. For an old computer whose hard drive cannot be wiped, removing the drive and keeping it or having it destroyed is the safest choice.
The most useful step is usually the first one. Pick a single suggestion, try it for a couple of weeks, and then decide whether it is worth keeping. Small, steady improvements last longer than ambitious plans that are hard to maintain once everyday life gets busy again.
It also helps to talk the subject through with friends or colleagues who have tried something similar. Their experience points out the details that guides leave out: how long things really take, which costs were unexpected, and which shortcuts turned out to be a mistake.
There is more to learn on this subject, and the linked website goes into greater depth. Treat this article as an introduction rather than the final word, and check any important decision against up-to-date, reliable sources before relying on it.