IMO, for cakes the view point which makes them appetizing is including their side walls. This means that one should shoot from the cake's eye level. Side walls of the cake show its inner fillings and therefore makes it more pleasing to the eyes.
In the case of cake, if one piece is chopped off and laid in the plate with the cake knife on the side (with bits of cake smeared on it) and cake dust visibly scattered in the plate, it can make one feel that that chopped off piece is waiting for to be eaten.
For the cooked vegetables lowering the POV won't help IMO, since there is nothing to see on the sides except the walls of the bowl!
Shooting from totally over the top of the bowl also won't make much sense since that way we'll find the food staring in our eyes.
For bowl of cooked vegetables, a better POV will be from slight up the walls of the bowl. Also, showing steam is a must. It makes the food look fresh.
Combining the cooked vegetable bowl with rice or bread (as per requirement) makes it look like a complete meal ready to eat.
Example: The small bowl of steaming curried kidney beans surrounded in the proper circular manner with steaming rice, and salad decorated on a side with yogurt bowl, is considered to be a delicious Indian cuisine.
Also, in case of certain kinds of cooked vegetables with curry, the main vegetable isn't easily recognizable. In these cases one option is to lift the recognizable vegetable part in a bigger table spoon and hold it slightly above the bowl (with curry dripping from it).
In this case, it does make sense to focus on the tablespoon part and slightly blur the beneath curry bowl (in order to make the vegetable recognizable).
Showing a little bit melted cream on the top of ice creams may trigger lip smacking, since the human brain may signal that lets eat it out before it melts further.
Also, placing a tea spoon on the right side of the bowl with some ice cream dripping from it, may sound inviting. In this case the part of ice cream held in the spoon should actually be taken off from the ice cream in the bowl. The sliced off corner of the ice cream in the bowl should be visible. Slicing from right corner would help since majority of the people are right handers.
Cold drinks are most appetizing when they are cold.
One way to make them look cold is to show the water (formed by condensation) on the outer surface of the bottle.
Also, IMO it makes sense to shake the bottle a little so that little broth forms up inside the bottle, since freshly opened drinks do have some broth while drinks when kept open for too long don't have any.
Choose a really juicy mango. Wash it thoroughly.
Let the water droplets stay on the Mango skin.
With the help of a peeling knife, peel off the 3/4 part of the front face of the mango [from top to bottom]. The peel should not break and in fact should be left hanging.
Also, squeeze the mango a "little" bit so that some drops of juice start appearing on the its naked pulp.
In every kind of food it is necessary to show its texture. i.e if we don't know what we are looking at we won't find it appetizing!
The plates and bowls in question should have a light coloured design. Bright designs may distract attention, and pure white (without any designs) may look boring.
Also, blurring a part of food is NOT too appetizing IMO since our eyes are used to visualize food as a whole. I mean if the food is tasty I want to see it whole.
The text and numbers on the canned/bottled foods shouldn't be in focus at all in the picture since they distract attention and also appear like advertizements.