What method(s) have proved most successful for you?

I can't really single out one method that works best. I'm much happier with a combination of methods.

• I've been a member of Perlmonks for close to six years. I just finished a period of visiting only occasionally, and I'm now back to reading and posting more often. Sometimes searching for an area that I'm working on will provide me with a two year old post that exactly answers my question -- fantastic! Sometimes I have to ask around.
• I've been going out to Toronto Perlmonger's meetings for about the same amount of time. It's like taking a post-graduate course -- with that many bright people in the room, there's bound to be some really interesting comments. The beer afterwards is fun as well.
• I've used the #perl channel on IRC intermittently, though more often over the last year. IRC is a weird animal -- don't take it too seriously and you'll be fine -- but keep in mind that there are also protocols and customs, not unlike Perlmonks. Even just hanging out and answering the odd question is cool -- and sometimes a question will be posed and answered that is really useful information. It can also get pretty noisy.
• I surf through CPAN looking for stuff -- keeping in mind that if I need to choose between something that was updated last week and something else that was updated in 2002, the newer package will usually win.
• I spend lots of money on O'Reilly books. Tim O'Reilly has been a supporter of Perl for some time, the O'Reilly books (with a few exceptions) are solid, amusing, well written reference books. My copy of the Camel is well-thumbed, and I continue to learn new stuff -- for example, I'd always known about positive lookahead, but never needed it until a few weeks ago. A bit of fiddling around and I had it working fine.
• When I can, I love to go to YAPC and immerse myself in Perl for three days. It's very neat to meet some of the folks in the community, and hear them explain their thinking behind a feature, a module, or the entire language. And, of course, there's the opportunity to drink beer.

The things that I don't bother with are

• On-line tutorials; and
• Certifications (useful for HR people and managers who don't program -- but that's a whole different flame war).

I guess that's because I consider myself pretty well-versed in Perl -- I don't know everything, but I know enough that I can confidently take on most projects. I'm still learning about all of the various modules on CPAN -- there's a lot of very cool code out there.