Am not sure of the legal issue here... as far as I'm aware filtering is a grey area. I tend not to pass the first car in a que so as not to gain road position... but this may be no more than a superstition on my part.
How?? Slowly and carefully. Remember, people can do the most random things. Be visable. Don't be in a rush.
What do you do / have to do??? Take great care. Only go if you are certian not to get stuck.
Where?? Where is safe and you feel confident. Obviously blind bends and very narrow roads are no-no's. Use common sense is my advise.
