Most B schools evaluate the applications holistically. The various parameters on which applicants are evaluated are undergraduate Academic performance, GMAT score, Work experience (both duration and quality of it), extra curriculars and any other special achievements which can help the candidate earn brownie points.
On an average B schools assign the following weightage:
Undergraduate Academic performance : 10 %
GMAT score : 20 %
Work experience (both duration and quality of it as seen through letters of recommendation): 20 %
Application & essays : 20 %
Extra curriculars : 10 %
Interview : 20 %
As indicated, 40% weightage is on tangibles which can’t be changed in a short time or can’t be changed at all. Rest 60 % can be done better ( GMAT score, essays and interview ) and can increase your chances drastically.
When B schools evaluate applications they give marks on all the parameters and calculate the weighted score.e.g. if an applicant gets 80 on undergraduate Academic performance, 90 on GMAT score, 60 on Work experience, 50 on Application & essays & 30 on extra curriculars ( all out of 100), the weighted score is 80X0.10 + 90X0.20 + 60X0.20 + 50X0.20 + 30X0.10 = 60 ( out of 80 , interview score not added).
Now top N students are given interview calls based on these scores. After interviews, the interview scores are added to the above score to calculate the total weighted score and again top M ( # of seats) students are given admission offers.
Disclaimer: This above analysis is based on talks and inputs from adcoms and students of different schools and profile on inputs class for various years and not on data released by any school.