Whenever you drive it, let the engine sit for a minute or two, and then drive it gently until it warms up.
If you want to take it to another level, you could bother to make sure that the car is decently clean before you let it sit for a week. For example, if you drive your car one day and there is some bird poop on it. Clean it rather than letting the car sit for a week with the bird poop.

 

If you guys notice, when you start the car after not driving it for like a day, the little meter is actually below the "C" (Cold). What I do is, I let the engine sit there until the meter is just a bit above the C, then I start driving it gently until it has reached normal operating temperature for like a minute or two. As I understand it, even though coolant temperature is warm which means the engine is warm, oil pressure has to build up as well.

 

This dude called me last week, from Infiniti (not my dealership, the company directly) to ask me how I like my car and if I had any questions. I asked him how to warm it up...in worst-case scenario, like if it's really cold weather and I had to park my car outside (my car sleeps outside during the college week (Mon through Thurs), unfortunately). He said to just turn it on and start driving...he said it doesn't do harm to let it sit, but it doesn't help for the car to just sit there. He said the best thing to do, no matter what the situation is, to just get in the car, turn it on and immediately start driving it. If the engine is cold, then drive gently until it warms up, and that's. I still like to let my car sit at idle for 30 seconds, but I'm sure the guy is completely right....we can just start the car and start driving.