If you absolutely must info dump, here are a few suggestions to make it more palatable for the reader.
Have a character who must learn the information so someone explains it to him.
In Jasper Fforde’s ONE OF OUR THURSDAYS IS MISSING, Thursday Next is in charge of an apprentice who follows her around at her job. She explains a lot of the technical elements important to the story to this apprentice. The info dumping isn’t subtle, but it is at least integrated into the scenes, and the give and take between the characters makes the info more digestible.
A another saving grace is that the apprentice and her knowledge of these technical elements become an important part of the final part of the book.
Never begin info dump dialogue with “As you know.”
Many years ago, this was a prime way to info dump in hard science fiction stories. These days, if someone knows something, they don’t need it explained to them in detail.
If both characters know the information, they can still discuss it. Here’s how I did it in the opening scene of TIME AFTER TIME, a romance about reincarnation. The hero and heroine’s guardian spirits are talking.
Celeste's expression softened as if she were trying to reason through a solution to their problem. "Thinking of all their lives.... It's strange how some of the same patterns and events occur in each one."
Although she knew the answer already, Walter prompted, "They're the same people whatever life they're living. They need reminders and lessons to reaffirm their strengths and fight their weaknesses."
Celeste grabbed his wrist. "That's it, Walter. A way to give him a will to live. Remember Gerard?"
In both cases, however, the info dump isn’t massive, just a few paragraphs or pages of explanation.
I have also seen bits of factual info like diary entries and quotes from other books used, most often at the beginning of each chapter. Some work, others do not, depending on the reader and the cleverness of the entry. The biggest disadvantage to this type of info dump is that the reader must pull himself out of the story each time, and that can mean the loss or disinterest of the reader.
However you info dump be very sure that this is the only way for the story to work, or you risk boring your reader.