Three factors that shift the supply curve

Firstly, it can not be due to a change in price.

So:

1. Improvement in technology (allows you to make more in the same amount of time).

2. Increase in capital (more machines/buildings means you can make more supply).

3. Changes with regards to the number of suppliers.

Taxes/subsidies/tariffs, price of other goods and change of recourses are also possible answers.