I just go by the look, smell, taste method. I look at it and if it looks gross (mold, slime, etc) out it goes. Then I smell it. Meat smells BAD when it goes south. Finally if it passes both the above then I taste a little. If it tastes fine I treat it as fine. Works for everything except tilapia fish. They smell/taste slightly mouldy to me even when fresh cooked!
Also if you realize you aren't getting around to using something up there are two options to extend it's life. Wrap it up and throw it in the freezer (yeah this might effect the texture but thats the only 'bad' thing about refreezing something) or reheat it. Heating kills off the bad bugs and kinda resets the clock on how long it will stay safe.