How big is your business? Which industry are you in? How computer savvy are your employees? Are you going to integrate your suppliers as well? How much do you want to spend on IT?
Do you want to manage it yourself, or outsource it?
There are a ton of ERP and CRM solutions out there, with many great free and open-source ones. You'll have to try them out and decide which one is best for you.
I was evaluating some ERP systems for a manufacturing business I was planning on launching.
I tried Apache Ofbiz, but I found it too confusing, with not much end user documentation.
I also looked at Dolibarr, and have found that much easier to use.