Choose an ERP package that is industry-standards based
Look closely at maintenance costs
Evaluate your processes and decide if changing them to fit a particular ERP suite would be beneficial.
Discuss a vendor's stability with the vendor representatives and outside experts
Find out how much customization assistance the vendor will offer
Be efficient in contract negotiations
And finally you must remember that you can't get everything you want. Do accept that there is always going to be a functionality gap. Usually, you have to let10% go. If the gap is more than that then you must look further.
