Firstly for example, if you are interested in Marketing do some job in any organisation which requires Marketing Executive or sales. this is the basic job which you will be offered for a graduate. starting a career with sales will give u indepth knowledge abt the market and also it helps u to increase ur interpersonal skills. work atlest for 2 years. then do MBA in top 50 colleges. in the mean time u study for ur exams viz..CAT, MAT, SNAP & XAT.
AND NEXT THING IS About business schools, u take any top 50 business schools u need to clear entrance exam, then follwed by GD N INTERVIEW. If you have already experienced it will be an added advantage definately u will be given more points over non-exp. and it will be easier for u also becasue as you will be having a market knowledge and u can apply ur practical aspects in theory.
For companies also they look for students who have fair knowledge about market, good in acdemics and should be MBA from an reputed college.
If u look at all these aspects u need to work for atlest 2-3 years. Even i completed my BBA, CURRENTLY working in software co.as a Business Development Executive, i will work for 2 yrs then i will do MBA.