I will add my two cents…since I too am making a concerted effort to learn C4D after a couple of misstarts. How you start depends on how new you are to 3d in general or just new to C4D, but:
1. Get the Ann Powers book – by far the best book to introduce the scope of the app to a beginner
2. Start reading the manual – don’t expect to get much the first time through. Just too much there and not many examples and *lousy* index. The pdf is easy to search, but tough to read on line.
3. Do every tutorial you can find. I would start with modeling. The 3Dkiwi tutorials on C4D Cafe are numerous, mostly small in scope, and high quality. Great stuff and free.
4. Read the manual again.
5. Do a “model-a-day”. This app has incredible depth and scope. Only by using it every day will you get comfortable with the workflow, thought process, tools, etc. It isn’t a once a week thing until you get to know it cold.
6. Read all the forums every day and try out what people suggest. My scanned forum list includes: Creative Cow, C4D cafe, 3dattack, renderosity, cgtalk, postforum — these are a tremendous resource. They have challenges and contests that are fun to do and everyone seems to be willing to answer even the most newbie of questions.
7. Read the manual again and start looking at other books.
8. Patience….Rome wasn’t modeled in a day or as the first project. There are experts in these forums on modeling, types of modeling, animation, character animation, motion graphics, textures, lighting, staging, etc. It is very easy to get overwhelmed and frustrated. You can’t know everything — you are always going to be learning. It is so easy to get taken in by the stunning work produced in these forums — “….but I want to make something that looks like that!….” — and then get totally frustrated because the gap between where you are and what it takes can be huge.
9. Persistance….I am constantly thinking “I am so stupid” when trying to follow some of the models and forum threads. I just have to leave the computer and then come back and try again. I was actually up at 3am this morning trying to model something – couldn’t sleep – and actually had several epiphanies…..with about several hundred left to go!
good luck…btw, sanity may be overrated ! 😉