I keep a box of toothpicks handy - they're great for transferring paint (and mixing it, too). For the thinner, I use an eyedropper-type bottle as mentioned in another post. Before I got the bottle, I was using a small straw, which worked well but was pretty time consuming.
As for the amount, you'll need to play with it a bit depending on the type of paint and the effect you want, but I almost always go for a roughly 80-85% paint, 15-20% thinner mix on the palette; you really don't need much thinner for small dollops of paint.