Is there any checklist to configure before upgrade for better deciding?
Is there any checklist for it after upgrade?
I have used the Upgrade status module on the past to better understand how much work will be involved in upgrading a site from a mayor version to the next.
Also, depending on how many modifications, or modules you have, it will also make the process easier.
One more tip: Check the Drupal documentation, and remember Youtube is your friend.
Just follow these 20 steps for successful upgradation from drupal 6 to drupal 7. Steps are listed in this link https://www.drupal.org/node/570162.