Create a generic dropshadow Action

1. Go to File>New to create a new file, choose A4 from the Preset dropdown or whatever size as long as the dimensions are larger than the image you will be using. (The drop shadow will effectively enlarge your target image size).

2. Open the photo you want to work on, click and drag it onto your blank file and close then your photo file. If you wish you can select your photo layer and apply a border by clicking open the Add border folder, click the Action sublayer and click the Play button on the Actions palette.

3. Create new set as before but this time with the name 'Drop shadow'. Click Create new action and Record to begin.

4. Click the Add A Layer Style icon at the bottom left corner of the Layers palette.