ALE IDOC Tutorials and step by step guide:

http://sap-interview-questions-and-answers.blogspot.in/2012/05/sap-ale-idocs-interview-questions-and.html

http://www.globalguideline.com/interview_questions/Questions.php?sc=SAP_ALE_IDocs

http://www.riyaz.net/sap/beginners-guide-to-ale-and-idocs-a-step-by-step-approach/18/

All the objects created should be present on both source as well as target system(s).
Step 1 :
Create Segment:  Tcode WE31

Step2: Create Basic IDoc type – Transaction WE30

Step3: Create Message Type in WE81

Step4: Link Message Type and Idoc Type in WE82

Step4:Define Logical Systems and Assign Client to Logical System – Transaction SALE

Step5:Maintain RFC Destinations – Transaction SM59

Step6:Define Ports – Transaction WE21
Step7:Maintain Distribution Model – Transaction BD64

Step8: 

To generate Partner profiles automatically you may use BD82 or go to BD64 and use the menu path Environment -> Generate partner profiles

• Otherwise, you may use transaction WE20 to create a partner profile