Repeat the reactions until you can do them completely.Let's look at the practical part of studying. Filling in Part A is not difficult, but it does start the reactions off in the proper direction. The problems get progressively more difficult. I suggest you plan to repeat problems several times. Think of it like any sports team. Do you need to practice? If the coach tells you what he wants you to do, do you need to practice it? If you cannot do Part C, then I predict when you are given a new and different problem, then you won't be able to solve it either. My experience is that many students made photocopies of Parts A, B and C so they could repeat it several times. Optionally, you could just write each exercise over on a blank sheet of paper.
A further note on the repetition. I cannot appeal to everyone equally with how your brain will respond to this. I cannot say with absolute certainty that being able to repeat the steps in a reaction provides you with the logical understanding of what gives a reactions its impetus. There is a magic that must take place between writing one and many examples in which your brain "gets it". It is my belief that you cannot get it before you can write a product of a reaction even if by rote memory. If you know what will happen by rote memory, you will have the foundation to apply that memory to a new problem.
Some books and instructors make it easy and emphasize the similarity of one mechanism to another (I did). That is the reason the reactions are grouped by mechanism. If you can do one, it will help to do the next because they are related. (If you photocopy a page, do all of the problems on the page. I have tried to make all of the problems on a page to be related to each other.) The more mechanisms you know, the easier it is to learn a new mechanism. You will see patterns (which is what our brains are really good at). If your instuctor does not, then you will need to expend more effort. However, I believe the book is laid out so that you should be able to easily do them on your own.
If you have questions on problems, you may post them on my web forum at www.curvedarrow.com. If you need help with finding problems that match your textbook, ask me and I'll do my best to help you. If your textbook has a reaction that I did not cover or you do not recognize the similarity, I will try to help with that as well. I tried to make mechanisms understandable, but I did not write a guide book individualized for every textbook, but as I learn which reactions A Guide to Organic Chemistry Mechanisms may be weak on or how to correlate them to other texts, I can help you.
I suggest you do page 1. If you have a good understanding of resonance structures, you can skip the remainder of Chapter 1. If you would like a refresher, go through it as well. Chapter 2 shows how to predict acid-base equilibria, if you understand this, you can skip it. Chapter 3 is nucleophilic displacement, Chapter 4 ...
First, I cannot underemphasize the need to understand the meaning of the curved arrows. Part A starts with only the curved arrows. As you fill them in, be certain you understand that the curved arrows are a description of how the electrons are moving. As you go to Part B, you must rely on the logic of Part A to rationally solve Part B. Part A must have been correct! If you can do Part B, then you have the basic groundwork for Part C. You could go back to Chapter 2 to see how I made the acid-base reactions to also be an exercise with curved arrows in that chapter. I sought to re-enforce the connection between the curved arrows, bond making and breaking, and English sentences. (While I can easily connect the arrows themselves to the chemical reactions, adding English sentences to the curved arrows may help you.)
Unlike when I used the book in my class, you must study on your own. If you have any questions, feel free to ask them. Because I have a sense that some students don't know what to expect from the book and what they must do to learn organic chemistry. If you can do the problems in your textbook without difficulty, then obviously, this book isn't going to help that much. However, many students are lost as to how to solve them. Reaction mechanisms are a rational method to solve new problems. Many students don't understand what or how to learn them. This book shows you how.
I want to repeat my advice for the start. In A Guide to Organic Chemistry Mechanisms, the same problems are presents at three levels. Experience teaches me that some students can skip Part A, but most students cannot write out Part C completely with one attempt. If you cannot write out Part C in A Guide to Organic Chemistry Mechanisms, especially after doing Parts A and B, then you cannot write the mechanism for a new problem either. Similarly, if you can write out all of the mechanisms, you will have an easier time in solving new problems. It will also take less time to solve them in your homework. It is the handyman rule, "The first time takes the most time because you must learn the most, after that it become easier and easier." That is where A Guide to Organic Chemistry Mechanisms can really help. It will save you time in connecting the first time problems.