A few points to remember

1. If you want to change the fiscal year start month, and your company follows the Gregorian calendar year, then use standard fiscal years
2. It is not possible to disable custom fiscal years once enabled. Enabling custom fiscal years has impacts on your reports, forecasts, quotas, and other date-sensitive material.
3. Once multiple currencies are enabled for your organization, it is not possible to disable them.
4. The Sharing button may appear on an account detail page even though your sharing model for accounts is Public Read/Write, if your sharing model for related opportunities is Public Read Only.
5. By default, Salesforce uses hierarchies, for example the role or territory hierarchy, to automatically grant records access to users above the record owner in the hierarchy.
6. It is not possible to include high-volume portal users in sharing rules because they don't have roles and can't be in public groups.
7. The sharing rule is always used to open up the access. By
8. It is not possible to delete standard profiles in Salesforce.
9. If you select the Read-Only checkbox under object Field-Level Security, then the visible checkbox will automatically get selected.
10. You can see the last 20 entries under Setup Audit Trail. If you wish, you can download the last six months' data for your organization.
11. Using permission set, we can only open up permission and cannot restrict them.