In setting SAP up properly, the first thing you want to do is map out the processes which drive your business. Talk to your business users, and find out exactly how they operate their processes, and what they need most from SAP to do their jobs efficiently. I would suggest you take a look at SAP help, so you can let your users know some of the things SAP will provide for them. (If you don't have SAP help installed on your system, you can go to the SAP help website http://help.sap.com
, but it only provides support from version 4.0 on - they recently removed their 3.x documentation). Once you understand your company's business processes well, you will need to do some more research in your SAP system to find out how you can match what SAP provides to your processes in place. This will be your greatest challenge if you do not know SAP well. In order to configure the system, use transaction SPRO. In order to correctly set up the processes for sales orders, accts payable, accts rcvble, etc, set up the config in SPRO as best you can. Once you have done this, test the changes you have made by executing the appropriate transaction to create a sales order, etc. and verify that the system behaves the way you expect after you have set the configuration. You will find that SAP is divided into modules like FI/CO, MM, PP, SD, Logistics (of which SD is a part), Project Systems (PS), Basis, etc. In configuration, you will find that each is fairly separate from the others, but there are places where they overlap. For instance, when you set up a G/L account in FI, often you will need to map that account in other areas, like in SD for pricing, or in MM you will need to assign the G/L account to a goods movement type so that when you do a goods issue at delivery, a G/L account receives its proper posting.
A book that I found helpful for configuring areas outside my expertise is:
SAP R/3 Implementation Guide - A Manager's Guide to Understanding SAP ISBN 1-57870-063-9
It is helpful in that it will tell you in general what SAP will provide. It will also help you to figure out how to configure the system. Though not always explicitly - it does in many places point you in the right direction. You can use it no matter what version you are on. I have found it useful for 3.1, 4.0, 4.5 and 4.6 SAP. If you follow the menu path system->status anywhere in SAP, it will tell you exactly what release you are running.
Hope this helps. More detailed email@example.com