I have previous experience in a different field and now i have to apply for software fresher job..should i mention my previous experience in my resume? Should i mention the percentage of marks in schools and graduation?
Typically, no, unless they specifically ask for it.
As for previous experience in a different field, I'd consider it for two reasons. Firstly if there's a gap in your employment history. Secondly, if you can talk about it in an interview.
The average tech resume is a page. At the end of the day, your qualifications matter more than the breakdown of your grades. Did you pass with honours? Add that. Did you get a D in one module and a gold star in spelling? Less interesting.
Consider as well that you're writing a resume for someone who's going to be skimming over it, and might not be technical. Keep it simple, focus on qualifications and skills, and you ought to have an easier time.
As for grades? I tend to bring a copy of them to an interview on a first interview in case anyone asks. I found that its more for "does he have the degree" than "what's his grades" in many cases.