I use P&W BMW in Shadyside, but my car is lease from A&L BMW in Monroeville. They have always offered great service and have an online appointment setting center. You just create a login, enter your VIN, and then select what work/services you need. A calendar comes up showing the dates and times available and you choose one along with your preferred service advisor. Afterwards you get a confirmation email.
You also get a reminder text/email the day before, and when your car is ready for pickup you receive another text and/or email letting you know.
I personally always ask for a loaner so that I don't miss any work. As long as you schedule a few days ahead of time you will always get one (you can specify if you need one in the online system). I just used one of their loaners today while they changed the oil on my 335xi. All of their loaners are now 328xis, but they used to have 5ers, 7ers, and X3/5s but people were abusing the cars too much.
Current: 2014 Ford Focus ST
2011 Jeep Wrangler Sport
2008 E90 335xi