Make sure that you count it correctly then put it into an envelop and fold the envelop close.  When she shows up you can mention it or just leave it in plain sight.  If she is going to ask about it, she will.

Re:Donation etiquette

I count it, fan it out and place it on top of a towel next to some massage oil and condons on the night stand in plain view ... that way there is no confussion as to what my intentions are ....hobby safe hobby well hobby all you can be

Anytime you're seeing a lady for the first time, you can expect her to sit you down for some chit-chat for 5 minutes or so.  She wants to size you up, make sure you're not LE or a crazed psycho.  While you're chatting, pull out the envelope (I prefer the type used for ATM deposits that's clearly from a bank) and when there's a pause in the talk, casually slip in "excuse me, can I put this here for you?"   A pro will glance at it and say thank you.  Some will pick it up and excuse herself for a second to go count it.  Don't be insulted...ladies get stiffed more often than you think and she doesn't know you.

Put the ca$h is a plain white envelope and place it in an obvious place, like leaning against the ice bucket.  Another acceptable method is to place the ca$h in a greeting card and hand the card to her with a "I want to wish you a happy birthday."  It doesn't have to be a birthday card.

put it in plain white envelope in very plain sight, away from my other personal belongings, so it obviously stands out. If the room has a desk, I'll keep the desk clear and put the envelope in the most accessible front corner.  Or something similar, though usually not on the nightstand if there is a more conspicious place.  (When I first started I read about the white envelope and that is how I've generally done it ever since.)  If I forget to take along the envelope, I just lay it out without the envelope. I only had one lady do anything with it before our time together was over, and she was a ripoff.  Must be I looked decent to them, or perhaps it was just their way.  Doesn't bother me if they count since I can make a mistake as well as anyone.  If I tip at the end, I'll slip it into an envelope with a thank you card.

I think Joercny's idea about using an envelope from cash dispenser is neat, too.

Some ladies want to check it some don't.  Some will polietly excuse themselves while your chatting and go the the table where you dropped it for some quality "me time" with the envelope.  A few want it after, most at the top.   But if nothing's on the website just drop the thing and see if you get lucky.

I had one lady have me through it on the dashboard when I picked her up.  (sexy)

In addition to all the excellent advice already given, I would also suggest using large bills.  I usually leave C-notes fanned out on the table/dresser/nightstand/etc.  It allows her to easily size up what you put down at a glance.  I feel that it helps put her at ease that you're not going to short-change her.  And seeing that you've ponied up, there's less or no need to even mention anything about money (which we've all learned in PayforPlay 101 is a good thing).