The way to change the default quantity to add to cart for all items is as follows:

1) Navigate to System > Configuration

2) Click on the Inventory tab under Catalog

3) Expand the "Product Stock Options" section

4) Click on the "Add minimum Qty button" next to the "Minimum Qty Allowed in Shopping Cart" field.

5) Select "All Groups" in the dropdown

6) Set "Minimum Qty" to 1 (or any number that you want all items to default)

7) Click on "Add Minimum Qty" button

8) Save Config to ensure it saved the value in as the default

9) Clear cache and possibly reindex.

This feature is driven by Counterpoint customer groups, so for example, you can set up a default entry of 1 for your retail customers, and a default entry of 12 for your wholesale customers.