Well, there's imperfect and perfect past tenses, but for haben you'd probably want to use imperfect. Imperfect is more common when written, but haben just sounds weird in perfect. ich hatte; I had du hattest; you had er/sie/es hatte; he/she/it had wir hatten; we had ihr hattet; you [pl] had Sie/sie hatten; you [fm] had/they had
It depends on the verb, and on the meaning.
"Ich fand es leicht" means that you found or thought something was easy.
"Ich habe es leicht gefunden" means that something was easy to find.
So, that's just one example. With most verbs, when you're speaking, you'll use the perfect tenses. But, there are some very frequently used verbs like gehen, kommen, finden, ... where you'll use both, and which one you use has an impact on the meaning.
If you'd like to read more on this, check out this guy's blog:
This is a link to the fourth post in a series on the past tense, but this one specifically deals with when to use which, and provides lots of examples.