different ways of making a field mandatory?

There are 4  ways of making the field mandatory are:-

1. Page Layout:- Field can be made mandatory from the page layout when it needs to be made mandatory for a set of users
2. Field Level Security:- Field can be made mandatory from the FLS when it needs to be made mandatory for all the users in the Organization and even from the API’s
3. Validation Rule:- Field can be made mandatory from the Validation Rule when it needs to be made mandatory for user who is using the same Page layout used by other users
4.  Before Triggers: we can also make a field mandatory using  before trigger

Salesforce.com recommends using the Page Layput option for making the field mandatory.