Re: What's an info-dump?
"Well, original poster," said Toby, relaxing in his chair, "as you know, we are both writers in the field of speculative fiction, or, as some call it, SFF. You're asking me what an info-dump is because you've been writing for some months and are now worried that you might have inadvertantly committed this error, am I right?"
Toby began to type. Good thing I've spend so many years working in a range of office environments, where I picked up these typing skills, he thought, as he set to work.
Basically, anything that fills in story gaps artificially and, as HareBrain says, in such a way as to break credibility, is an infodump. Areas to look out for include character backstory (especially as to explain things that crop up later), setting politics and technology.
It can be got around mainly by keeping the downright explanation to a minimum. "Jim woke at 5 am to find his wife gone" tells us that Jim has a wife. Similarly, if Bob says to Jim "Hey, are you coming to the Space Commando dinner and dance tomorrow?" we have a fair indication that they are both linked to the Space Commandos. That's fine. However, if Bob says "Since we're both Space Commandos and served on the Zeta Reticuli campaign, where we won medals, we should go to the annual dinner and dance tomorrow", we're in infodump territory, as the information is introduced in a forced manner.
Rarely, it can be done blatantly with success. However, this is rare and I wouldn't advise it. I have recently read a book called The Peshwari Lancers by SM Stirling, which contains a whopping great infodump in a dream, which to my mind doesn't work.