While developing the workflows, one has to make use of 
interface, methods, data types , reference types etc. The 
technical specification should carry about the changes made 
in interface, methods, datatypes, etc.

Check area menu swld.

Also try swdm t-code as it has lot of examples.

WorkFlow in simple: The state of an object changes from one 
state to anather with Human activity.
There must Human Activity involved. 
Example from agent to operational manager to next higher 
manager.

Agents submits a paper to be approved by his operational 
manger.
Agents object state is being changed by his operation 
manager with some interface/GUI etc.

go to the link
http://www.sapmaterial.com/workflow_sap.html.
it has a perfect example to start with  screnshots.hope it will help you.

Workflow is the flow of information from one person to 
another and so on based on certain hierarchy at a corporate 
level. Thus a work flow is needed to pass on right 
information to right person on right time. The work flow is 
set based on the business rules of a company. This 
information may be in form of an email or an e-document.

E.g.

1. Leave request.

After an employee applies for a leave permission through 
system, the application request is routed to the 
appropriate immediate boss or supervisor for approval. The 
supervisor or the boss can view the leave request after 
logging in the system and can either approve or reject the 
leave request. If the leave is approved, the employee 
receives the mail in his system informaing that the leave 
has been approved. Thus the work flow gets closed over 
here. But if the leave is not approved and the supervisor 
requests the reason or cutting down number of days for 
which the leave has been applied for (for e.g.) to the 
employee, the employee accordingly replies through his 
system.

2. As in case of e-procurement, the generation of purchase 
order for certain amount needs to be approved through some 
higher level authority before it is send to vendor for 
procurement. the purchase order then passes to the 
authority and based upon his/her inputs the purchase order 
is routed to vendor or gets rejected.

To summarize the above examples, workflow is nothing but 
the flow of information in the corporate hierarchy, usually 
through mails or e-document. The entire wrokflow need to be 
set up based on business rules and scenarios of the company.