Every description you give of the surroundings should be reflected in and colored by the emotion that the character is feeling.
example:
He walked into the kitchen and found it a mess. The dishes needed done, last night's burnt dinner was still on the stove and the towel was still thrown over the back of the chair.
vs
He felt like the towel thrown over the back of his favorite kitchen chair, limp, lifeless, and yellow. A quick glance around the kitchen brought him back to last night's events. The dishes, still dirty and in the sink, were they mocking him? Daring him to do something about it? Dinner still on the stove, a dinner that was supposed to be wonderful, and yet lay there incinerated. Yeah, last night was about as much fun as burnt steak.
Emotions color how we see things. It adds depth to our surroundings and a feeling of reality.
on plot development and thickening you can actually start at the end, and ask yourself, what made this happen. Then write that event down. and ask ok, what made that happen. and write it down. and so on back to the beginning.
nothing grips the reader more than not knowing what is happening in the initial paragraph. There's a fight going on to start off, but why? what the hell is happening? the reader will wonder.
my god there is so much to tell. don't have a character tell his wife his background in the middle of an arguement, by this i mean things that reader should know, but that she already knows.
"yeah? well i wish i'd never seen oyu that day when you were in the red dress leaving your mother's house and getting onto that bus with a copy of war and Peace under one arm and and a black purse filled with stolen diamonds."
to which she replies:
"yeah well who would have thought that 3 years later while i was eating a donut at max's diner that i would meet you while you were gay and didn't want to have anything to do with me because your mom shot the dog and you didn't trust women?"
it's a bit exaggerated i know, but you'd be surprised how often i find this kind of atrocity. ( i don't read clive cussler anymore)
last but not least. subtle foreshadowing. each chapter should foreshadow something for that character, wherther it happens in the next chapter involving him, or one 4 chapters away. It keeps the reader interested, and they don't even know it.
sorry about being so long winded, but these are some tips i have found along the way.