not sure how to add exception handling

hello guys , I have this subscribe page with the following code , anyway....I want to add exception handling for it , but am not sure for the best way to do that , I checked over the internet for sql exception handling , and all of them were just to write ( cannot open connection ) , but I dont want that...I want something better , in another pages when there was sql error I used to save everything I want in a text file in the catch block , but that isnt that much useful here ....I wish someone can help me for this

using System;

using System.Collections.Generic;

using System.Linq;

using< ...