Here's the way I usually do it...
Rule 0.5: "Flow of the game is king."
Players are allowed to bring the PHB (or equivalent SRD sections) to the gaming table. If they are using 3rd-party stuff (cleared by me), they bring photocopies of only the pages relevant to the character/abilities they are using.
A player is permitted to "appeal to the PHB/SRD" if he feels I made an incorrect ruling regarding a spell's effect or what the proper procedure for a grapple is or whatever... but he has to be able to pull the rule up within about 30 seconds or we move along. The rationale is that characters would be familiar with how THEIR abilities work (the PHB) and how "normal situations" like combat, trapfinding, etc. work (the PHB) but NOT about how monsters work or about how magic in general works (specific spells that they can cast, yes, magic in general, no).
Monster stats, et al are the province of the DM and cannot/should not be challenged (the "player knowledge is not character knowledge" rule) in the first place.
In order to keep things running smoothly, I make rulings on the fly if I don't know the rule. But any time I make a "ruling on the fly," I tell the players such and make a note of it. Between sessions, I research the actual rule behind the ruling on the fly, and before the next session discuss any differences with them (i.e., "it worked this way last time, but I checked up on the rule, and in the future, it will work this other way"). If they think I "missed something," they can bring it up after the session as well, and I'll research it.
I'm open with my players - I tell them I don't know everything, and I'll try to do my best, and when I'm unsure, I'll research it... but nothing gets changed "retroactively" (too many continuity problems) if I make an erroneous ruling - only "from this time forward." This cuts down on any DM-player tension, because they know "I'm on their side" - but I'm not perfect, and shouldn't be expected to be so.
It's worked for almost 20 years for me - I've never had a "problem player" at my table (and some of the players at my table have been problems elsewhere).
--The Sigil