I always place verbs with the "~たがる" ending (called a helping verb?) in the present continuous, or past continuous state:
I am having trouble with using the non-continuous tenses (行きたがる、食べたがった) to express myself. The meaning of "~たがる", as I understand it, lends itself too much to being in a continuous state of "wanting to do something" or "having wanted to do something".
I kind of see my strategy as always using the continuous tenses to express myself. And, if I ever hear the non-continuous tenses, then I can understand (but, I cannot remember ever hearing the usage of a non-continuous tense).
Examples of when "~たがる" cannot be used in a continuous tense (the "~たがっている" and "~たがっていた" continuous tenses) would be very helpful to me.