If you're meeting at a hotel which does require a key card, then you can either meet at a place nearby and go into the hotel together, or you can to meet in front of the elevators at exactly the same time. Be sure to tell each other what you'll be wearing so that you can spot each other quickly!
Yeah, hotels that have elevators that don't need key cards are best for this hobby.
Even with hotel elevators that require key cards, I've found that most SPs are very good with timing on meeting the pooner at the elevator, quite often I'm only waiting less than a minute or two at the elevators of a hotel. However, there have been a couple of times when I'm waiting close to 15 minutes by the elevator because the SP wasn't actually ready to leave her room even after she asked me (she called my cell just a couple of minutes before the rendezvous) to meet her at the elevator at a certain time, I felt like an asshole waiting by the elevator especially if the hotel front desk staff have a clear view of the elevators.
One time, a visiting SP from TO was staying at a busy downtown Vancouver hotel that required a key card and get this, she doesn't head down to the lobby to meet pooners. So she tells me to get on the elevator with hotel guests and when one of the hotel guests uses a key card to hit the button to her floor. Initially I was skeptical, but I was impressed that it actually worked on the very first try. I got into a packed elevator, must of been seven or eight people, the moment one guest used a key card, everyone else on the elevator hit the buttons to their respective floors. However, I'd guess not all hotel elevator key card systems work this way.