Hey there! :D
To find a vertex on a graph, you would need to look at where the line stops. This place where there is a distinct curve or stopping point and at least one line is going infinity in one direction is the vertex. The graph is much easier than any other method, because it is visual. If I was looking at the vertex on a table, I would see (especially on a quadratic) if there was a pattern to the points. Most points are opposite of each other, so it can be helpful to look at a pattern. In an equation, a parent function can help to see where the vertex is, as well (for quadratics) finding the line of symmetry with the equation to find the vertex. (-b/2a) The strategies are very different, some are easier than others. For example, I would much rather look at a graph for a vertex then do an equation to find it. Some involve looking, seeing a pattern, and others solving. They are all very different but can all be extremely helpful!
I hope this helps!
~kaikers