Over the past several days I've received several reference checks for which providing an accurate answer was like pulling teeth, with back and forth emails, phone calls, guesstimating, etc.

When you offer a provider as a reference, saying something to the effect of "I'm John Doe, here's my phone number, she knows me"...chances are she may not (especially if you've only met once or twice and a period of some months or even years ago).

When you're with a provider make a quick mental note of a couple of things.  What hotel are you meeting her in?  What was she wearing when she opened the door?  Did you say something really funny that made her laugh?

I nearly never remember names and I have no use for storing phone numbers...but I will probably remember that Celtic cross tattoo on your back or that we share a love of classic cars.  

When you offer a provider's name just qualify it really quickly with one little tidbit that will make her recall your time together.

I don't mind providing references real time, but when it becomes a task, over a span of hours, multiple phone calls and an irritated provider mad that I can't complete her screening process or a dismayed client talking to me as though I'm a bad provider for not remembering our appointment eight months ago...it gets a little hairy.

White List referrals are an awesome starting point if you write reviews and don't mind having them on your profile.  
Date-Check is also amazing - just shoot a little email post session!  It totally simplifies the whole process and your references can be checked day or night!