When you work on SAP projects keep in mind that 99,9% of your questions can be answered on official SAP resources.
That’s why I put most useful resources into that list.
You can provide your links in comments/answers
SAP Help Portal(documentation and tutorials)
Information about SAP Notes(S-User required)
Quick Sizer tool – Quick Sizer is a Web-based tool designed to make the sizing of SAP Business Suite easier and faster. It has been developed by SAP in close cooperation with all platform partners and is free of cost.
SAP Comminity Network – portal with blogs, wiki and forums
If something wrong with standart functionality then you can create an incident to SAP support team
SAP Software Download Center. Download SAP products that are associated with your S-User ID.