Non smartass answer: typing, lots and lots of typing. The thing that I had to do with Java was do projects that forced me to learn Java libraries and idioms. If you build a web app that uses a database, and does some disk IO, you'll learn a lot about how Java is used.
Also, I recommend Eclipse if you're looking for an IDE. And get familiar with the Java libraries available from Apache.
Unless of course, ooh cool, Adobe came up with a killer app by combining PDF and Flash in to one thing. Have they already done this? Have I missed the boat?
Internet victories seem to always arise from companies that do one small thing well, an unencumbered product that's new or better than the other guy in a very crucial way. Unless you stay better (Google) or manage to build a suite of stuff that people get accustomed to or dependent upon (Yahoo!) you will fall by the way (Hotbot, Altavista, all the other poor schmoes I'm forgetting).
In the online space, Microsoft has been unable to foist stuff on people, try as they might, and they're too un-nimble to build a toehold technology/site that people fall in love with and then build on that. Everything they do starts out encumbered. In that same space Yahoo survives because early on they built their initial success at ordering the web (before searches did it better) into a mail and portal product people came to rely on. It looks like now Yahoo is merely in a position of holding on to mail and portal clients as long as they can before Google chips them away.
I use Yahoo for: (1) the Yahoo mail plus service with disposable email addresses; this I live by, but use it only for online accounts and stuff I don't want coming to my Gmail account; (2) weather; they rely on Weather.com, and present a three-day forecast that I like better than Google's weather. I don't think people are discovering or switching their homepages to Yahoo.
Gluing Yahoo onto Microsoft doesn't seem to to add anything to either company. How is MS going to build business based on Yahoo's slipping market share? How is a desktop monopoly going to help Yahoo gain share when that desktop monopoly has never succeeded at that? Microsoft typically crowds and clutters web pages with ads and MS branding. Yahoo already has busy-ness and clutter down pat. Both Yahoo and Microsoft could be good if they were to think creatively about how to be good: focus on online services that are better than what Google's strategies will allow (NOT search), or, in MS's case, hone instead inflate their OS (vid. Vista) and Office applications. But Microsoft has demonstrated again and again that they are constitutionally incapable of doing these things with their own or anyone else's technologies.