Thank you for using the Jiskha Homework Help Forum. These 3 verbs are usually used in the 3rd person singular and plural. That is NOT to say the forms can't be used.
gustar = gusté, gustaste, gustó, gustamos, gustaron (to please)
te gusté = literally I did please you but translated you liked me!
me gustó = I liked ONE thing or one thing pleased me
me gustaron = I liked two or more things or two or more things did please me
importar = importé, importaste, importó, importamos, importaron (to be important)
encontrar = encontré, encontraste, encontró, encontramos, encontraron (to meet, find)
The good news is that 3 verbs are regular -ar verbs in the Preterit