Tools:

• Gateway Error Log
• Gateway Client
• Gateway Tracing Tools

Recommended Articles:

• ABAP Connectivity - SAP Gateway Wiki
• SAP Gateway Community
• SAP NetWeaver Technology Community
• Tag: SAP Gateway
• SAP Gateway - Guided Answers - KBA 2537427
• SAP NetWeaver Gateway 2.0 - Known Constraints -
  SAP Note 1574568

Related Pages:

• Using OAuth 2.0 from a Web Application
• Configuring Remote Systems in SM59
• Create an RFC trust relationship between 2 SAP systems

Video Tutorials:

• SAP Gateway: Introduction
• SAP Gateway: Technical Overview