Michael Sandel's public lectures about justice might be a pretty good start, if a course isn't what you're opting for. it's very accessible but asks some tough and questions:
I would suggest having discussions with philosophically interested friends over a beer or two about interesting questions big and small such as for example, "how do we know anything?" or "is it wrong for a necrophiliac to practice what he desires if it was done fully in private and with a fully sanitized and well preserved cadaver that has given consent before death? if not, why not?" You might not get anywhere, but it's pretty fun with the right company, and you get a taste of what philosophers have to get good at.
You can talk about some of the reasonably down to earth questions given in introductory lectures like Sandel's or the ones linked to by Josh1billion, or any thing else that might interest you and who ever you're talking philosophy to. As long as at least one of you keep asking a genuine 'why?', you will end up in a pickle (sometimes an interesting philosophical pickle). Resolving and spotting these holes in reasoning, I think, is an important part of the training of a philosopher, no matter which area of philosophy one finds most interesting.
But if you're looking for a rule book, like they give in a programming and such, familiarizing yourself the form of valid arguments will be as close as you can get to that. These will help with spotting where people's reasoning might have gone awry (or are deliberately sneaky.
I don't have a good suggestion for books on argument forms (anyone?).
I also found talking to grad students about their thesis a good way to get up to speed about something I'm not too familiar with. They might appreciate it too, if you ask them the right
read the suggested readings of intro course and talk to philosophically inclined folks about what puzzles you will be good too, as it will force you to explain yourself.
what marry didn't know is something that almost everyone reads, almost everyone will form an opinion on but it's actually not that easy to establish your position solidly.
Last but not least the Stanford Encyclopedia of Philosophy is a philosophy student's best reference (for all those confusing terms). It's free, online and the articles are written by professional philosophers.