Bumpiness and Poles are not difficult to understand. All you need to do is don't think about it!
Do what is required, do what is needed and the rest will fall in place which is another mindset you should keep in mind.
Look at the mouth and eye.
1: Do what is required, Do what is needed.
What is required here is a circular loop and what is needed is a SMOOTH surface and there I have it. It does not matter where the Poles are since they don't interfere with "What is required, what is needed" (aka The Stroke concept). This is one way of looking at Poles and the majority look at it this way by the way. You can choose to look at it this way or you can choose to look at it from a Flow perspective or even both. If you're not sure where a specific pole should be then start collecting Wireframe references.
There's not much to talk about Bump/Pinch in regard to static modeling since it's self-explanatory but I'm sure it will surface again when you get into UV and Bone. For now if a pole is bothering just unpole it and move it elsewhere. There, no more problem.
Extrude Loop / Spiral Loop
One thing to keep in mind when you get into edgeloop is the Spiral Loop. Once you break the extrude Loop you'll going to get the Spiral effect and when you do, don't try to rewire it so it goes in a circle because it won't work. I did an experiment where I broke the extrude Loop to get the spiral effect yet at the same time retain the extrude Loop – this is not possible. Beginners tend to use the Extrude Loop since it's easier and requires no knowledge of Poles. Now that you know how to manipulate poles you should start breaking the extrude loop to form the
Spiral
Loop since the SL is more organic and it blends in with other areas of the mesh. Beginners extrude and leave it the way it is (not professional) and you can tell by looking at their mesh.
Remember to use wireframe references if you're unsure of what you're doing.
Pole and Topology
C:
From my experiments and understanding, the C-Topology is easy and fast and because of this it's suitable for Cartoon models (or even Creatures). Cartoon/Creature starts with "C" so this is one way to remember it. Trust me, you'll love the C-Topology once you model Manga/Anime characters! You'll be amazed at the speed and efficiency of this Topology (assuming that Unpole is now second nature to you).
X:
Do not limit yourself to Cartoons/Creatures, you can actually use the CT on human heads and speaking of Human heads, X is mostly used by professional artists. It gives you greater control and defines the head better.
S:
If you're bored with CT and XT try ST. This topology is not that common but it's there for anyone who wants to get fancy with Topology.
That's all there is to Topology (ST, CT, XT) and out of these three you can mix/combine and get a variety of new ones (unpole) but it's all based on one of the three so pick one and start from there. In the future I'll show you a wireframe version of these 3 Topologies for now you must collect wireframes elsewhere since I have only touched the C.
Generally speaking, when you look closer you'll see that the CT has no pole around the cheek and that the XT has one Epole between the ear and eye. This says that a pole or poles defines a Topology.