You should hire a project manager with experience in ERP implementations who DOES NOT work for your company or the partner/vendor supplying you with the software. Contract a 3rd party entirely. This is the only way to avoid conflicts of interest and find someone who will keep both parties straight and honest. Your partner will fight this tooth and nail, and you may resist this internally yourself, but if you talk to companies who have done this, it is a winning strategy all around.
The most challenging part of any ERP implementation is the resistance to new ideas and ways of doing things. In some cases, you should change your business processes to match how the software operates, and in some cases you will want to change the software to match your process. You will in fact find cases where you do things a certain way only because your old software made you, and new software will be an opportunity to refine and optimize old processes.
You should strive whenever possible NOT to modify the new software, regardless of how easy is appears to be or they claim it can be, but there will be cases when you simply must. The exception is reports. You will write tons of reports to get your data the way you like it, and for the most part reports are low cost and low impact and survive upgrades pretty well. Code changes are where you pay over and over, as not only are they much more complex but they must be re-considered at every upgrade.
The single most important quality in your team leaders is the ability to ignore the phrase "that will never work". If you selected software that fits your organization, it will work, and what doesn't readily you can make work with some effort.
The single most important quality in your team members is time. ERP implementations are big and complex and require many hours each week of time above and beyond standard responsibilities. Out of the gate, your teams probably won't have a whole lot of extra time, or face it, you'd have fewer people. But time is exactly what they and your project needs, and most projects fail for exactly this reason above all others.
Joe's boss isn't going to yell at Joe because he spent all afternoon working on customer issues and entering orders and couldn't find the hour he needed to write or test that new procedure. Your project needs Joe to have that hour, and away from his daily duties. Setup an isolated lab dedicated to your ERP project, and unplug the phone in the room. The ERP project will never be the priority on its own, you must make it a serious priority. If it is the last thing on everyone's mind, it will never get done. The last thing never does.
Don't set a go live date until it's obvious that you're very close. Under no circumstances consider going live unless you are absolutely ready. Companies that go live with new ERP systems that aren't fully baked.. go out of business. American La France comes to mind first. Read about what happened to them. If you're not prepared to sacrifice time for quality, you should not start an ERP implementation.
Good luck to you.
