Dropping subject when conjugation is unambiguous
Apologies if this is a frequent question, I did some searching and didn't come up with anything.
In Spanish it's common in conversation to drop the subject when it's either A) already established by the context of the conversation, or B) when the conjugation is unambiguous. For example, one could say either "Soy un hombre" or "Yo soy un hombre" and either would be acceptable.
Is the same true in German? I would be surprised if it were not, but if I've learned anything about German thus far, it is that I should expect to be surprised/confused by its rules. :)
It is certainly done - I don't know if I would say it is done frequently. I guess it's a question of what counts as frequent, but from what I know of Spanish (which is nothing by the way :P) I think it is much more common in Spanish than in German to omit the subject - at least in cases where the conjugation is unambiguous. In cases where the subject has been named earlier it is common to leave it out; but here it also depends on how much earlier we're talking about, for example:
„Ich habe gestern mit meinen Eltern heftig gestritten und
ich bin dann noch eine Weile gefahren, um mich zu beruhigen.“
The yellow "ich" there would be more commonly left out than in, though if the first and second parts were separated out in conversation, it would be more common to put the yellow "ich" back in; for example:
„Was hast du gestern gemacht?“
„Naja, gestern habe ich mit meinen Eltern heftig gestritten.“
„Oh nein! Worum ging's denn?“
„Um mein Studium.“
„Ach, Mensch. Nicht das schon wieder. Und was hast du danach gemacht?“
„Na also, dann bin
ich eine Weile gefahren, um mich beruhigen zu können.“
Taking another example however:
Du Siehst ja gut aus!“
There the yellow "Du" would be more commonly left in than out.
Obviously I could be smoking my socks here and be completely wrong, but that's been my experience at least.
Hope that helps a bit.
*Edited for correction
The principle rule for building grammatically correct sentences in German is that you cannot leave out pronouns! The only admissible exception is, when the sentence is composed of more than one partial clauses that share this word, so that it would cause a repetition, as in the sentence quoted by AdamKean: „Ich habe gestern mit meinen Eltern heftig gestritten und bin dann noch eine Weile gefahren, um mich zu beruhigen.“. In this case option without the repeated word is even preferrable, though the longer one is still correct. In spoken language you will find further deletions, such as „Siehst ja gut aus!“. But you usually would not find those written.
Although it's possible. Example: "Wie habe ich das gemacht?" - "(Es) sieht gut aus."