IWB carry takes a little getting used to. It will feel somewhat uncomfortable until your body gets used to it. Once you do get used to it, the only time you'll notice the gun, is when its not there. Give it a good try and dont give up to soon. Once you get used to it, I doubt you'll use any other method. It really is about the most concealable way to wear a medium to full size gun.
Probably the most common, and most concealable spot, its right around 4:00-4:30. The gun nestles in that crook just under your rib cage and under your arm, where your arm hangs naturally and it helps protect and conceal the gun.
This is the spot I'm refering to...
Some people like to go up a size or two with the pants to allow for the gun and holster. I personally prefer my normal pants size. While it does feel a little snug when you first put the gun and holster on, it soon feels better, and the gun tends to not move around as much, as your pants help hold it in place. If you should decide to take the gun off, your pants still fit.
A proper gun belt and decent holster are also big helps in making things more comfortable. The Wilderness Instructor type belts are some of the most comfortable, and are adjustable through the entire range. You dont have to be a tad loose or a tad tight because the right spot is in between two holes, you get a perfect fit at any given moment. The only downside to them is, they are pretty identifiable as a gun belt.
I've tried a lot of holsters over the years, and have settled on Blade Tech's kydex IWB holster, and Milt Sparks Versa Max II leather holster. Both are comfortable, but I use the Blade Tech more, but especially in the summer, as its impervious to sweat.