Past Tense in Dutch, Questions and Sentences
How do I know when to use the "ge" version of the verb at the end of a sentence?
And when asking a question which way is correct (I'm try to say Did you forget to Skype yesterday)
"Vergeet je gistern Skype?" or "Heb je gistern te skype vergeten?"
And is using "Heeft" or "Heb" the same as "Do you" or "Did you" in English

Any help is much appreciated,

Danny

Question

Past Tense in Dutch, Questions and Sentences
How do I know when to use the "ge" version of the verb at the end of a sentence?
And when asking a question which way is correct (I'm try to say Did you forget to Skype yesterday)
"Vergeet je gistern Skype?" or "Heb je gistern te skype vergeten?" 
And is using "Heeft" or "Heb" the same as "Do you" or "Did you" in English

Any help is much appreciated,

Danny

Answer

There are no clear rules on when to use the voltooid tegenwoordige tijd (hebben/zijn + ge..), but I would say that in most cases, you want to use this tense.

You sentence should be: "Ben je gisteren vergeten te Skypen?". We use Skypen as a verb in The Netherlands. "Heb je .." is also correct, but I don't hear this often.
"Vergat je gisteren te Skypen?" (onvoltooid verleden tijd) is gramatically correct, but makes less sense.

The onvoltooid verleden tijd ("vergat") is used mostly for storytelling. "Ik vergat te Skypen, en toen...".