A few points to remember

1. Use permission sets to enable Lightning Experience for a set of users.
2. After Summer'16 release, we can have 5 active processes on the Lightning Professional edition.
3. It is not possible to change standard objects' and fields' API name.
4. We can add custom fields to standard and custom objects in Salesforce.
5. We can have a maximum of 40 lookup relationships on an object.
6. We can have a maximum of two master-detail relationships on an object.
7. Each Salesforce organization can have up to 100 external objects.
8. When we delete a custom object, it appears in the Deleted Objects list for 15 days, from where the system administrator can restore it.
9. Salesforce doesn't allow us to delete a custom field that is used in a roll-up summary field on another object or reference in Apex and Visualforce pages.
10. If a custom object contains more than 100,000 records and you want to delete it, then first delete an appropriate number of records and then delete the object.
11. By default, Lightning Experience is now enabled for all standard profiles.