My absolutely pet peeve is long straight hair with no layers cut in. It has absolutely no movement and no volume at the roots. I like to keep the bottom half of my hair quite long (past shoulders) while snipping off the top half of my hair around ear length. This 'mushroom' shape means hair looks big on top and sleek underneath - and can be exaggerated with extra back combing.
Fixing your layers at home can be done surprisingly easily and a professional effect can be created with the help of a hairdressing blade. This sounds like it could end in a bloody mess, but salon suppliers sell blades with plastic handles and you can hold this tool as you might hold a kitchen knife. I have found a really cheap one £1.99 from this direct supplier (picture right).
The blade ensures that the ends are slightly uneven and look more natural than if you cut straight across with scissors. While a hairdresser can create this effect effortlessly with cutting techniques the blade is a 'quick fix'. By angling the blade you will feel it either cut very sharply, or it will appear to drag with resistance meaning it is blunter and not cutting as sharply.
To cut in the layer pull the desired section up in the air directly above your parting. For neatness I tie the section below up tightly in a bun so it doesn't interfere. By applying the blade in this position the hair that grows nearest the parting will be shortest and the hair that grows nearer your ears will be a about 2cm longer (creating that layered look).
Once you decide how much you want to lob off, push the grooves of the blade against the hair as if you were combing it. The 'teeth' on the blade will mean the hair isn't sliced off 'uniform' at one length. Slowly wriggle the comb pulling it towards the ceiling. You will feel tension as the hair is grabbed and cut. Soon the blade will have severed through the chunk of hair and you will be left holding the chopped off bit in one hand.
Brush the hair back up the air one more time. Does it look straight / even across the top or have you pulled tighter one side than the other? If the latter repeat again and be consicous about keeping the blade level throughout.