How to 'pick' herbs?

[shivvy]

I keep parsley, mint, thyme and basil on my kitchen window sill and use them in lots of recipes.
The plants seem to like the position and get topped up with water regularly as they are right beside the sink.
I am interested in how best to pick the leaves of each plant so as to maximise their lifespan.

I currently pick the basil and mint leaves off the stem although the plant does tend to get a bit tall with smaller and smaller leaves.
I use the parsley and thyme by cutting the whole stalks off at the base which means that I just end up with short chopped stems poking out of the soil!

Could I be doing it differently so that the plants last longer or produce more leaves?

Thanks.