hold the pick parrallel to the strings but dont force yourself on it slowly your hands will adjust themselves in a comfortable position.every guitarist has his own ishtyle
But in doing so, shredding will become a near impossibility. And raking and sweep picking may be rendered ineffective. You need to incline the plectrum a little. Besides, holding the plectrum parallel to the string is not how your hand/fingers will normally stay. Usually the guitar is slightly inclined upwards, whereas you hand rests on the bridge or forearm rests on the body. That way if your hand drops down straight, your fingers holding the plectrum, it will always be at a slight angle to the strings. If you try to make it dead parallel to teh strings, you are just straining your wrist and tiring it.