As a quick impromptu smoker all you need is two trays of the same size, quite deep ones, and a mesh of some sort. The wire rack from a grill tray or a cooling rack are ideal and it needs to be slightly larger than the two trays.

Put your wood shavings in the bottom of one of the trays and damp them slightly (a fine spray bottle is good). Put the wire rack over the top and place the items to be smoked on it. Turn the other tray upside down and place over the wire rack.

Put the whole lot over a gentle heat and smoke away to your heart's content. Remember though that when I do this I have the luxury of a industrial kitchen with a good extractor system so I suggest you open windows and/or doors and take the batteries out of your smoke detector, or be prepared to choke a bit.

WHy stop at fish? Chicken, duck, venison, in fact just about anything can be smoked and IMHO is all delicious. Just make sure that if smoking chicken it's hot smoked enough to cook it. I also of course hold no responsibility for anyone going down with food poisoning as a result.