Snappy: The most common way is to use the simple present, especially if the "want" has just happened. The progressive can be used in conversation, for emphasis, if I have been thinking about it for some time in the present. Normally, an adverb of emphasis would be used.
Situation: I am in a restaurant, reading the menu. I say to my friends: What do you want today? I want a ham
Personally, in normal situations, most of us would simply say "I have wanted a LCD TV for a long time, but it was too expensive...". Wanting - sounds a little too unuaual, although it is still grammatically correct.
This is my perspective: "Want" is a human emotion, or shall we say 'desire" which before it's actually fulfilled it always implicatively exists. In that