Try to have each scene that's plot-related say something about your characters. And if you want a "character" scene (say, MC breaks up with his or her loved one), find something in there that you can add that relates to the plot.
I try to write to this advice, but I'd just qualify it a little to say: have every scene say something NEW about your characters. I don't need to see several scenes that demonstrate the same personality trait or quirky habit - once something has been established, either develop it further, or assume the reader will remember it for whenever it becomes relevant to the story.
I do like character establishing scenes though. I was trying to come up with a way to show the reader what a nasty piece of work my Big Bad is, so I had him stage a fight to the death between a pair of his own prize hunting hounds and a baboon to entertain his dinner guests. When the baboon ripped them to pieces, he was more annoyed at losing the bet than losing the two dogs.
It might have been a little 'kick the puppy', but one reader said that made her hate him more than anything he could have done to the MC.
To make the scene pull double duty, I also had a messenger arrive mid fight to convey an important plot development. There's nearly always something you can add to a scene to make it more relevant.