Holding the plectrum.
The plectrum, or pick, is available in various grades or thickness from supple to quite firm.? It is recommended that you get yourself a handful, they are very cheap, and try the various grades.? It is best to start with medium, say .73mm,? until you have decided what suits your style best.? You will find that the softer pick, say .38mm,. will give a crisp, bright sound, bringing out the higher frequencies on an acoustic guitar and the harder pick will give a more rounded, mellow sound.? The softer pick is easier to use if you get into heavy strumming particularly with both down and up strokes as it slides over the strings more easily.?
To hold the pick correctly hold your hand out straight, side on, then close your fingers into a loose fist until you can place you thumb? on your first finger between the tip and the first joint.? Slide the pick in between you finger and thumb till the pointy bit is showing by about 1/8th to 1/4 of an inch.
You will adjust your hold to whatever feels comfortable for your hand and your style but this is the starting point.? You could ball your hand into a loose fist or leave the other fingers open which is fine provided that you don't touch any other strings accidentally.?
The very tip of the pick is used to pluck the string down.? This is why you only need a little bit showing.? You do not want to bury the tip 1/2" past the string because you will have trouble plucking it.
Now pluck all of the open strings one at a time until you feel that your movement is smooth and all open notes have the same volume.? In other words you are not plucking one string harder than the others.? Make sure that you do not obstruct any strings with your right hand.? It is very easy to accidentally touch a string with the palm of your hand so watch for this.? The pick should slide smoothly over the strings in a downwards motion and not pluck the string outwards.