Here are a few tips on picking technique for the mandolin that I have learnt from my teacher and books.
What type of plectrum?
The mandolin is usually played with a plectrum (otherwise known as a pick). Plectrums come in different shapes, sizes and colours. The most common is the teardrop as shown below.
Plectrums also come is different thicknesses. The thicker the pick the more stiff it is. Mandolin players usually use medium(~0.7mm) to heavy(>1mm) thickness plectrums. The gives you greater control over the pick and a better tone. Plectrums are fairly inexpensive (about 50p in the UK) so as you get more experienced you can experiment with different plectrums. My preference is DAVA plectrums as they have a tractor grip which stops the plectrum slipping out your hand.
When playing notes the plectrum should start at a very slight angle to the strings. It is a wrist action that actually plays the note as shown below:-.