It varies a lot from person to person. Generally speaking, methods that give one big hit tend to feel more intense than methods involving lots of little hits. One hitters and gravity bongs are popular methods to get the most 'bang for your buck' out of a limited amount of herb. Some people swear by bubblers and bongs, though, and I had a friend in college who insisted that he got WAY higher hitting a dry piece or joint and actually thought THC was water soluble until I proved to him otherwise based on how inefficient bongs and bubblers seemed to him.
So, my advice is pretty simple: if you have a small amount you wanna conserve and don't know what works best for you personally, gravity bongs are a good bet - easy to make, designed to take big rips with small amounts of material and generally having a strong reputation in this area. However, next time you have a decent supply of bud, you should experiment with various different smoking mechanisms to find the one that works best for you. I personally find the best balance of effectiveness, enjoyability, convenience and conservation to be a simple one hitter or "bat."