Placing a call through Google Voice is simple. If you're using the Google Voice app on an Android phone, you begin by choosing one of three options -- use Google Voice for all calls, use it for only international calls or don't use it at all. From there, you use the key pad or choose one of your contacts, just as you would with any phone, and the number you're calling will display your Google Voice number. There isn't much to it.
Now if you want to use your Google Voice number from a landline or non-Android-based system, you go about it differently. One way to do it is by calling your Google Voice number then signing into your voicemail. Once you do that, you'll be prompted with a few options, one of which is to place a call. Select this option, dial the number and your Google Voice number will be the one placing the call. Another way to do it is through the Web site or mobile site. When logged in, select the "quick call" field then chose the phone you wish to call from. You select the phone you wish to use (assuming you have more than one set up), and Google Voice will call you at that phone. Once you answer, the service connects you to the number you're calling.
Now let's see how you can use it for business and maybe even save some money in the next section.