I advocate not reading them from a web site or book. I suggest you make your own list or lists.
Your book may contain a table of aromatic ring substituents, their directing effect, and whether they are activating or deactivating. I believe memorizing that table is anti-chemical and prone to student errors. I believe a more general method of predicting directing effects by arenium ion stabilization or de-stabilization is easier to understand and apply. I prefer to do this by examining the resonance structures of the ground state substituted benzene rings. Those resonance structures that provide a negative charge in ortho and para positions are o/p-directors and react faster than benzene. Those with positive charges in ortho and para positions are meta directors and react slower than benzene. The halogens are an exception to the reactivity scale as they are o/p-directors, but because the halogens are reluctant to donate electrons are o/p-directors that react slower than benzene.
This example is one of chemical principle. This is something that should make chemical sense and you can derive it or apply it as needed. A consequence of applying this chemical principle is that it will enable you to find similar principles to be applied to other reactions. If you make your own list, you will enhance your ability to understand chemical properties and reactions.