not being pretentious -- you will actually need it. I've been reading this book on and off for about four years now, and wish I had started with a notebook from the beginning.
don't get discouraged if some passages are boring -- make a note of them and just power through them.
it's so, so worth it. I think I'm probably really only "getting" 10% of this book but it's still incredible.
Like watching Tarkovsky straight from Michael Bay is not something I'd recommend, I'd tell them to watch some Nolan for contemporary, then Kubrick and stuff before going for Solaris. Is there an equivalent?
other than that, don't be too afraid -- Infinite Jest is intentionally complicated and convoluted, being a bit confused is part of the experience. even if you aren't quite sure what's going on in every chapter, the writing is gorgeous and funny even on a sentence-by-sentence basis.
You'll meet one character, then move on to another character, then return to the first character four hundred pages later. You'll read footnotes on footnotes that refer to other footnotes. There will be plays on words that appear on page 20 and then are reprised on page 600. Extended metaphors are introduced and return without warning.
Just start reading it, and if it gets too hard, put it down a bit. It's still a book for entertainment (the whole story is _about_ entertainment), so don't treat it too much like it's homework. just have fun with it :)