How to use hot keys to launch applications in OS X
Along with the standard ways to open programs, you can set up key combinations to quickly open your most accessed ones.
If you need to quickly launch a program or two in OS X, you can use the Launchpad interface, or, perhaps more quickly, find it in Spotlight, or use a link in the Dock. However, a third option that might be particularly useful for some utilities is to bind them to a hot key shortcut.
For instance, common utilities you may access when troubleshooting problems in OS X include Activity Monitor, Disk Utility, Console, and perhaps Terminal. If you regularly access these or other programs, then you might wish to have them available at your fingertips, so binding each to a hot key may help.
To do this, you will need to make an Automator workflow that will open the desired application, save this workflow as a service, and then bind it to a hot key in System Preferences.
First, open Automator, and create a new Service workflow. Set the workflow's parameters (at the top of the window) to receive "no input" from "any application."
Next, search for and drag the action called "Launch Application" to the workflow area. Set the program to be opened from the drop-down menu ("Activity Monitor" in the example photo), and then save the workflow with a relevant name.
Finally, go to the Shortcuts section of the Keyboard System Preferences, and select the Services section. This section will list a number of built-in and third-party services available, and will also list the custom ones created in Automator under General. Locate the newly created ones, and then click the "add shortcut" button that appears when you select it. Now type your desired hot key; it can be anything but should be something guaranteed to be unique.
I recommend using Option-Command-tilde for Activity Monitor, since it is very close to the Option-Command-Esc hot key for Force Quit -- but any hot key that doesn't conflict with other assignments will do. Some options you might think about using for other applications are the Function keys (you may have to hold the Fn key to activate these), or sequenced hot keys such as Control-Option-Command-1, or Control-Option-Command-2, etc.
You can repeat this setup to create specific shortcuts to open for any additional programs you use.