The decorative pillows on a sofa or bed is a very personal thing. Some people like to be minimalists and just have pillows for function. Others want a variety of pillows in various colours and textures to make a grand statement, waiting to be admired at every passing.
Whatever your style, choosing what you love and are willing to keep organized is key. You may like the way a room looks with tons of cushions on a sofa or piled neatly on a bed, but if you're not going to make that look happen each day, is that really the look for you?
I recommend going through a variety of photos and seeing what combinations seem to catch your eye. And of course what doesn't! Hopefully some of these examples below give you the confidence to know what to go for.