A second tip for today: An easy one that I use frequently: If a file format (.jpg, for example) tends to default to a different application than you wish to use, (Preview, for example) follow these steps to open it with the app you prefer:

1. Select the file in the Finder (without opening it) and press cmd-I for a "Get info" window.
2. About halfway down, select "Open with" and a list of apps will appear. Select the one you want. (If the app you prefer is not in the list, scroll to the bottom to "Other" and you can locate the app on your drive.)
3. Close the Get info window and double-click the file. It should now open with the app you selected.
I find this method to be MUCH faster than opening the application first, selecting "open" from a File menu, then rummaging around the drive to find the file.