A healthy piece of plant material is not necessarily a useful cutting. The part capable of making a new plant depends on the species and the propagation method.
Before cutting, identify the plant and check whether the method uses a stem, leaf, root, scale or bud. A demonstration involving one succulent is not evidence that every houseplant leaf can reproduce in the same way.
Locate the structures you need
For a stem cutting, understand where its nodes are and which section the chosen method requires. For a leaf-based method, find out whether a stalk or a piece of stem must remain attached.
Prepare the container and growing medium first. Label the plant and the date, especially when several cuttings look alike after their leaves have been trimmed.
Keep one method separate from another rather than assembling a routine from unrelated videos. Water-rooted stems, dormant hardwood and leaf sections can have very different requirements. A cutting that stays green for a while has not necessarily formed roots or a new growing point. Check progress without repeatedly pulling it out of the medium.
Related reading: Types of Plant Cuttings: Stem, Leaf, Root, Scale and Bud.