Classical vs 'Modern Rock' structure

It may have been noticed, but as im not musically trained whatsoever, i tend to 'write' classical music, but in a modern way. for example; segmented parts often including an intro into a verse, with a chorus, etc, etc. Any advice would be greatly appreciated on how to write classical music properly. cheers

That's a scarily big question.

Read books, study scores, and listen to music paying particular attention to form. There's no simpler way, and I'd be a filthy liar if I implied that there is.

OK. Possible more pragmatic plan of action, a mere suggestion: Read some kind of "beginner" literature on form (Wikipedia is a good start if you want to stay at home), getting at least a rudimentary understanding of what terms like ABA form, sonata-allegro and rondo mean. Then (and this might be the most important step so far) listen to recordings of whatever music you fancy (and play music, if possible! If practically possible for you, just sight-reading through Beethoven, Haydn and Mozart sonatas at however slow a tempo is really good for you in many ways). Try to recognize what material the composer has to work with (themes, motives etc), how he (or she, though historically it tends to be he, but I digress) presents it, how he develops it. When and where and how he does what. This step alone, if done with the proper attitude, can take you a long way to understanding how music can be constructed and organized on a larger scale. If you like you can intersperse the act of listening with reading analyses, books on form, etc, but listening can take you a long way.