Beginners guide to BPEL

Have a look at the ActiveBPEL IDE. Also you can find a short 101 BPEL guide in Oracle. The demo is about Oracle's BPEL engine, but the source is general enough.

BPEL is just a way to build centralized control of disparate but interdependent systems from a centralized place.

Users can create rules, workflows and other control structures to make sure everything plays nice.

For example, say you run a school district; in particular, a school districts information infrastructure. Over the years you have accumulated a motley assorted group of hardware and software. For each aspect of your district; grading, attendance, bus routes, nutrition, payroll, etc, etc, you have various distinct software written in different languages by different vendors. Well, you have some overlap in your data and different end users use the different pieces of software and they expect it all to agree with each other - you use your BPEL system to be sure all the data is where it is supposed to be when it is supposed to be there.

You also have some processes that absolutely have to run after the successful completion of another process on a different system. You use BPEL to make sure those are coordinated. BPEL is all about centralized coordination and you probably don't need it unless you are in a large organization and lots of different systems.

This BPEL tutorial covers on how to write a BPEL from scratch.
Writing a simple WS-BPEL process for WSO2 BPS and Apache ODE

This article covers the IDE based BPEL process development. Developing WS-BPEL Processes using WSO2 Carbon Studio