Correct way to cut bed head

i have noticed that when i have my hair cut as well as using a razor the hairdesser cuts into (think notches) rather than straight across when it comes to using the scissors to take length off... and as well as using a razor uses thinnin scissors. The best cut i ever had was when a hairdresser twisted pieces of hair and hacked into the twists with a razor... so what the right way for cutting a bed-head or do they all complement each other as the different stylists i have been to all have a different idea.