通常求職信是針對報紙上招聘廣告而寫的。若此，信中須提到何月何日的報紙，有時工作機會是從朋友或介紹所聽來的，有時寫信人不知某機構、公司有工作機會，毛遂自薦。不論哪一種，求職信上一定要說明寫信的緣由和目的。
因此首先應該表明你是在何家媒體看到應聘廣告以及所要應聘的職位。參考例句：
1.In reply to your advertisement in today's newspaper，I respectfully offer my services for the situation。拜讀今日XX報上貴公司的廣告，本人特此備函應征該職位。
2.Replying to your advertisement into- day's issue of the(newspaper)，I wish to apply for the position in your esteemed firm。拜讀貴公司在今日(報紙)上廣告，特此備函應征貴公司該職位。
3.With reference to your advertisement in(newspaper)of May 2for a clerk，I offer myself for the post。從五月二日XX報上廣告欄得知貴公司招聘一位職員，我愿應招。
4.I wish to apply for the position advertised in the enclosed clipping from the(newspaper)of November 12.謹隨函附上十一月十二日XX報貴公司招聘廣告，我愿應招此職位。
5.In answer to your advertisement into- day's newspaper for a secretary，I wish to tender my services。閣下在今日XX報上刊登招聘秘書廣告，本人獲悉，特此應招。
6.Learning from XX that you are looking for a sales manager，I should like to apply for the position。從XX處得悉，貴公司正在招聘一名業務經理，我愿應招此職。
7.Your advertisement for a telephone operator in the newspaper of March 8has interested me，I feel I can fill that position。貴公司三月八日在XX報上刊登招聘電話接線員廣告，本人拜讀后極感興趣，相信能擔任此職。
你現在知道英文求職信中寫信動機怎么寫了吧?當然別忘了在寫完求職信的時候記得給旁邊人檢查一些再發送給HR.