Be it the hand, the leg or any other part of the body, the right hand side always, AFAIK, takes a higher status, preference or position in terms of positivity then the left.
For the right side:
- use the the index finger of the right-hand when touching the Quran during recitation*
- during ablution/ghusl wash the head, neck then preferable the right shoulder
- when stepping out of the house put your right foot out first*
- give alms with the right hand*
- angel on the right shoulder logs good deeds*
- in wassu wash and wipe right hand and foot first
- eat with the right hand*
For the left side:
- in all the above cases it is either left out, comes second or is used for bad things (angel on the left side log bad deeds)
- clean yourself with the left hand*
Why is this so? Is it Islamic, mythical or cultural ?
* don't know the authenticity of it