And to make it all more interesting, various rear derailleurs shift quite differently so there is no hard and fast rule and the same goes with the tooth profile on the cogs. Hyperglide teeth on rear cogs shift easiest as has been mentioned already. Uniglide cogs seem to shift better than Suntour to me as they have a twist on the gear teeth. A 5 or 6 speed will also be different than a 7 speed if we are just considering freewheels. Some of us feel that this is all part of the character of each individual bike and requires different techniques on an individual basis.