Congratulations, Amanda! Hope you are settling in - it is always disheartening to come on board when there are problems, but is a great opportunity to make a difference. Whenever I have a new manager, leasing consultant, maintenance supervisor, etc. come on board, I like to write a letter to the Residents introducing him/her to the Resident. These days, it's also nice to post it and a photo on the community facebook page. It need not be something elaborate, but it should say something about your experience, enthusiasm and that you are being supported by your management company.
If that did not happen, and it is too late in your opinion to do it, I would not talk about rule enforcement in the initial contact. I usually wait a couple of weeks, and prior to the new month/rent due date, I post on every occupied door and mail it (or email it) to every resident a letter about Policy, Procedure and that "although in the past, the rent collection policy may not have been followed according to company procedure, it will be beginning September 1, 2014 ..." Make every effort to add support language from the lease to reinforce the rules are right there in black and white and you will ensure that the property runs smoothly. Keep it positive and factual, short and sweet. You might consider including your Regional Manager's contact information, too, because from my experience, you usually have a few residents who like to test it out and want to complain that you are making them pay their rent on time - and how dare you.
If you have any other specific questions, feel free to contact me!