first of all to write an analysis of an advertisement one should have following things on his/her mind.
*Selecting the headlines and main points of the advertisement.
*Separate the main points and give an explanation to each of them.
*describe the usefulness of the advertisement to the audience.Because the analysis is based on the acceptance to the audience.Therefore,the writer should keep this matter on their mind.
*Comparing the advertisement to the other competitive products.