SAP HR Upgrade 4.6b to ECC 6.0

Dear All,

Presently i am in preparation phase of SAP HR Technical upgrade (4.6 B to ECC 6.0) from ABAP side.

I have stepwise process details but i don't have experience in Upgrade projects.

so Pls help me with

1. Check list to start with

2.Issues faced during upgrade

3.Precautions to be taken

4.Major objects to check

/ Lalit