Step 1: Start the Delegation of Control Wizard, select your user or group to delegate
Open the ADUC, find your domain tree and browse to the topmost level that you wish to apply user permissions (for example, 'Domain users' at my workplace), right-click > 'Delegate Control'.
At the Welcome dialog, click 'Next'.
At the Users or Groups dialog, click the 'Add...' button. You will be prompted to add a user or group to which you will apply delegated rights.
At the Select Users, Computers, or Groups dialog, either type the name of the object (use domain\username or domain\groupname for best results) or click 'Advanced'> 'Find' to locate your resource you wish to apply permissions to.
Once you've selected your resource(s), click 'OK' at the Select Users, Computers, or Groups dialog, then click 'Next' at the Users or Groups dialog.
Step 2: Delegate your task(s)
At the Tasks to Delegate dialog, you can select from a wide assortment of tasks to assign to your users.
***** If you ONLY want to delegate the reset password task ****
Verify that 'Delegate the following common tasks' radio button is ticked and select 'Reset user passwords and force password change at logon' and click the 'Next' button.
Continue to step 3.
**** If you additionally want to delegate the ability to enable/disable user accounts ****
Tic the 'Create a custom task to delegate' radio button and click the 'Next' button.
Tic the 'Only the following objects in the folder' radio button, and select 'User objects' and click the 'Next' button.
At the 'Permissions' dialog, select the 'General' and 'Property-specific' checkboxes and in the list below, check the following permissions:
Click the 'Next' button.
Step 3: Complete the Delegation of Control Wizard
Once you've finished delegating your tasks, you can click the 'Finish' button at the Completing the Delegation of Control Wizard dialog.
Now the users you delegated these tasks to should be able to reset passwords (or perform other actions you specified) on the objects in the OU where you set up the delegated permissions.