Dale Grote's Comprehensive Guide is the best companion to beginner's Latin that you can find - aside from a passionate real life teacher, of course! Note that it is not in itself a course. Grote's volume is specifically keyed to the classic textbook Wheelock's Latin. You could use it with other courses although the concepts might well be out of order.

Grote operates from three principles:
1) That one of the biggest challenges modern language students face is that they haven't received the grounding in English grammar that our parents and grandparents did. As a result, he spends a lot of time breaking down concepts in a relatable manner, and you can really feel the benefit of his lengthy career in teaching.

2) That many beginner's textbooks look at the language from the point-of-view of the teacher, not the student. Grote enthusiastically points out tips and tricks with a student mindset. His lucid, pragmatic, sometimes amusing voice is just what is required. He has figured out how to explain in-depth concepts in ways that make them completely transparent. This includes an acknowledgment (which textbooks rarely want to tell us) that some of the annoying aspects of learning an inflected language, which can seem like "extra work" (such as deducing whether a verb's stem has a short e or a long e) are actually necessary; that the heavy work now will make later life much easier.

3) Most importantly, he recognises that the Wheelock's textbook - for all its thoroughness and good humour - is, in many ways, quite dire. Don't get me wrong; I have warmed to Wheelock's in recent years, especially with the 7th edition. A committed student can get much out of the expanded collection of texts in that series. But it's fair to say that Wheelock's is aimed at ensuring even middling highschool teachers - perhaps those who don't have much Latin themselves - can teach the language in a clear, methodical way that's focused on getting students to exams. (Sometimes a student must learn Latin like mathematics; that doesn't mean teachers should teach it like same.) If you're American, especially, you probably won't have a choice; the textbook is the textbook. You can't expect your school system to switch to my beloved Cambridge course.

Grote will get you there. It's an addition to that course, teasing out concepts and reiterating what you need to know. (If you can find his old audio lectures online, which often include him talking through the questions in the textbook, you'll be in for a treat.) If you're not using Wheelock's, I don't recommend spending money on a new edition of Grote; but if you can find it secondhand, it's still a neat volume for a first-year learner. ( )