When playing guitar with a plectrum there are a couple of things to consider in order to get the best playing experience.
First, you need to decide what type of plectrum to use, as they vary in size. As a general rule, thinner plectrums such as the Jim Dunlop Nylon .60mm plectrum work best for lighter picking styles such as acoustic guitar strumming. Smaller and thicker plectrums such as Jim Dunlop Jazz III plectrum work better for harder picking styles such as rock and blues playing, where riffs and lead playing are more important then light chord strumming.
Once you have the right type of plectrum for your chosen playing style, then you must look at the way you are holding and using the plectrum. It is best to hold the plectrum at a 45-degree angle pointing towards the headstock, this helps with crossing over the strings as the angle prevents the pick from getting caught on the strings. Holding the plectrum at this angle also adds a slight ‘bite' to the sound, which can be useful in certain styles if music such as rock.
The plectrum should be held with a decent grip so that it doesn’t slip out of your hand however you don’t want to hold on to it too tight otherwise you can add unnecessary tension to your hand which can cause problems long-term.