As a fan of misty-type shots and meteorology, I might be able to give you a few pointers.
You need humidity, and lots of it, along with very contrasting night and daytime temperatures.
When it gets warm during the day, the atmosphere can "hold" more water vapour, but then as it cools down rapidly in the night, a lot of that moisture gets condensed into steam - you then get to see it as mist or fog.
Winds also need to be calm or at least very very light, if a breeze does get up then everything gets mixed up and you lose that lovely low lying mist effect.
You also need to know your "frost hollows", it has to be a valley where cold air sinks and collect into one particular point. As a result, the bottom of that valley gets shrouded in fog while the surrounding higher ground remains in clear skies.
Oh, and skies need to be clear so that heat can easily radiate out into space, thus encouraging surface cooling - perfect conditions for low lying mist to form.
But like I said, the key thing is high humidity. If the air is too dry (as what happens when winds flows in from the Continent) then there'll be very little in the way of mist or fog.
Usually Spring and Autumn time is best for this kind of thing due to the wide variation in air temperatures (gets hot by day but still can easily get cold by night).
Hope that helps.