What fruits are good to eat when dieting?

I'm on a diet, but I don't know how to eat fruit.
I heard that fruit contains sugar, so it's not good to eat too much of it.
I'm curious because I heard it's okay as a snack substitute.
I'm not sure if things like apples or bananas are okay.
Do you have any recommendations for fruits that are filling yet easy on the stomach?
I am also curious about how to control the timing and amount of food consumed.
I'd appreciate some tips for those of you eating fruit while on a diet.