I will hazard a try at a few practical recommendations. Feel free to disagree.
– Don’t be afraid of “main lines”. I spent 20+ years avoiding them because I was afraid of being out-booked. Then I saw a great quote on the Boylston Chess Club blog from Ubermaster David Vigorito, speaking to another expert: “I think you over-rate both your opponents’ preparation and the value of surprise.”
To David’s point, I have been playing the incredibly sharp, unbalanced, unsafe, bookish Alekhine’s defense for about three years now and I have never been busted in the opening. (It’s inevitable, yes, but the point is that it’s so rare as to not merit concern. Why not learn a real opening if that’s the case?)
– Get a good book. The Starting Out series is really quite excellent. I am told that Kaufman’s book is great and that Rizzitano is very good at providing clear explanations (and having seen a couple of his lectures, I am sure it’s true.) If you are, like me, a part-timer, you are going to live in this book for several years.
– But don’t memorize anything! Memorization is drudgery. What you are doing is learning about a set of positions that arise in probably four to seven major variations available to your opponent. You are learning common tactics. Common strategic ideas. Memorization is largely a by-product of this learning process. Where are the weak or strong squares for each side? Which pieces might you want to trade off, and why? You will eventually find a few lines where memorization is key. This is true in the Vorohnez line of the Exchange Alekhine. Eventually Greg K killed me and I had to finish learning theory until around move 18 to hope for equality. Not the first priority.
– Play through annotated GM and IM games in your opening. It doesn’t matter if they’re playing exactly your variation. Stop and ask a million questions. It doesn’t matter if you get all the answers right.
– Play it. You will never be completely ready. After maybe five or six months of playing a “sharp” and unusual opening online, I ventured it against a lower-rated player OTB. I won because I got a decent position from the opening and then out-played him (19 moves). After about a year, I played it against Denys Shmelov (2300 at the time). I got a decent position from the opening and the he out-played me.
Do you see what you’re doing? You can’t sit for two evenings and learn everything about the Panov Attack or the Schliemann Defense or whatever. You have to stew in it for a long time to learn anything. But you have to go ahead and play it and take your lumps.