I tried many different nipples, and had the most consistently positive results with Gerber's NUK orthodontic nipple which is newly designed to equalize pressure. A lactation consultant once suggested that I turn the nipple over so that the hole faces the tongue instead of the roof of my baby's mouth, but this did not seem to make a difference for us. Temperature is important. My baby liked his bottled milk slightly warmer than room temperature. Some babies prefer that the nipple be warmed slightly by holding it under warm running tap water.
Location can also make a difference.
I avoid offering the bottle in places where I usually nurse. Since I always sit on the sofa, rocking chair, or lie in bed to nurse, I found that my son was more willing to take the bottle if I started off standing or walking with him. I did, however, find it very difficult to be patient during this time. I felt it was important that my baby not sense my urgency or desperation. This particular problem led me to an important understanding about how much my baby needed me.