As I move from note to note in legato, I like to visualize an even surface over the top of my connected notes. It's as if I'm rolling out a carpet of air/sound over the music.
Let's hope, for example, that the family cat doesn't get rolled under that carpet...
A question you don't want to hear: "What's that lump doing under the carpet?"
The same is true with our legato...we don't want certain notes to stick out.
On the other hand, we don't want our music to be a flat, featureless landscape either. We need to imagine a carpet over a smoothly rolling hill. Perhaps something like this?
Ack, no, I can't go there...
How about this?
Ah, much nicer.