There are several fairly common ways to romanize. You have probably seen the Hepburn system, which seems pretty haphazard to me. Here is a chart of symbols and pronunciations.
Vowels are short and clipped.
Each of the 'symbols' given in this table last one 'beat' or mora . This means that each one of these romanizations lasts about the same time. In Japanese it is not the strength or volume of a syllable that determines accentation, but pitch changes. No accent on a word is indicated by a lack of diacritics. I will leave off accent markings unless what I'm talking about requires it.