When I start shooting those tall office buildings, I've realized couple of things. First, It's much better taking a more over-exposed image as an under-exposed one. When I checked each photo on my Nikon D3100 LCD screen, I've noticed that many of my images had a lot of noise. I shot all the images at ISO 100 in order to have little noise as possible. The problems is because I used Low ISO, my camera had to expose the sensor for a longer period of time, which lead to some noise patterns. I was able to actually get noise free images when using +2EV (or even more than that).
When I shot images at +0EV, I've notices that in those kinds of dark surroundings, where the only light comes from the reflections on the buildings, it's better to elevate the exposure compensation for at least +1.5EV. The most problem with that kind of shots, especially with entry-level cameras, is that you get a lot of noise in the dark areas of the image. Elevating the exposure compensation helped solving the noise problem. Of course later on you will have to tweak your images in photo editing software. That's another reason why I shoot in Raw and not JPEG - It gives me more freedom to tweak my image later on (especially when the exposure is a bit higher than optimal).
a faster shutter speed and minimize camera shake.
There are two other important things to note. First, you need to turn off you VR or IS (depends on which lens you use) when you mount your camera on a tripod. That will prevent minor lens movements as the lens image stabilization tried to stabilize an already stabilized camera (dough).
I also pre-focus before shooting. I put my lens on M/A mode and pre-focus on the building in front of me. After that, I moved the switch to 'M' so when I press the shutter button, it won't re-focus on the building. That's OK when you shoot at daylight, but at night, you will have a problem focusing in many cases. So what I did is to aim the camera towards a spot that had a good contrast and locked-in the focus. Then I had no problem shooting the same building in many angles, when staying in the same distance from the subject. If I changed the distance, I re-focus again and vice versa.
When shooting building, I've noticed that the Nikkor 18-55mm VR isn't wide enough. Because I intend to shoot more architectural type of photos, I have decided that it will be a good idea to have an ultra wide angle lens with me.
Editing My Images
When I came home (after approx. four hours) I uploaded the images to my computer to inspect the image more closer. I've found what I comprehend when I was outside, the well (even over) exposed images turned out to be much better than the less exposed one. I really don't like to see to much noise in the dark areas and it makes removing the noise very difficult in noise reduction software.
When I imported the shots to my favorite Raw conversion software, I boosted the contrast and played with the levels in order to come up with satisfying results (how I wanted the image to appear). In one image I did a very accurate selection where the sky is and applied some noise reduction to make the sky crystal clear without noise patterns. That worked amazingly well, and it's a must for those kidn of photos where a large portion of the image is sky.