Chances are these days any of the oil vitamin D3 brands sold in stores will work at raising your 25(OH)D testing levels. Most places with generic labels will have probably bought from the same production facility.
Personally, I buy Now Foods vitamin D3. It is well priced, and I happen to know the family that owns Now Foods. They sell at low prices and I recall when I worked in the food industry a decade ago that Now had a good quality testing department.
Since D3 is a fat soluble vitamin, you will want the fat form that is sold. Best to avoid the dry tablets.
Everyone is different on quantity needed. The average person will want 1000ius of D3 for every 25lbs of body weight. For example, a 150lb person will want to take 6000ius of D3. Of course not everyone is average so it is best to test. I personally aim for a testing level between 60 to 70ng/ml.
There are two types of vitamin D sold in the US. There is D2 which is the plant form of vitamin D. It is not used in the body as well as the animal form of vitamin D, which is D3.
With the mention about the sun, something to keep in mind is that when UVB rays strike our skin more than just vitamin D3 is created. There are around a dozen or so other substances manufactured too. These other items are not as well understood, but researchers are finding more and more about their importance to our health.
Recall seeing this article on Dr. Cannell's free newsletter the other day on the argument for some sun exposure.
"Proceed at your peril"
http://blog.vitamindcouncil.org/2012/05/21/proceed-at-your-peril/
snippet from his article:
Dr Cannell discusses the possible dangers of completely avoiding all UV light and how supplements should not be your only source of vitamin D.