Goto the list settings and create column.
Name the column as "Sticky", and choose as checkbox (Yes/No). We are going to give the option to the owner of the post, while creating the post whether it should be set as sticky or not.
Step 2 Create a View for Sticky posts
Goto the settings page and create the view and name its as "Sticky", set is as public view
Another important thing in the Sticky view is changing the sort columns. First sort coumn should be "Sticky", that is the intention of having the sticky posts. Sticky posts should be always shown on the top and then followed by the Last updated posts. So set the "Then sort by column" to Last Updated column. as indicated below. Step 3 Selecting the Sticky view
Whereever we are showing the discussion board, that is the List View webpart. Click on modify share webpart menu and change the selected view to "Sticky" which we created in Step 2.
Now we have the Discussion board ready with the Sticky option.
All the posts which are marked as sticky will be shown on top always.