Submission deadlines vary among papers, but formal etiquette suggests that you submit your announcement anywhere from three to six weeks before the wedding, especially if you're placing it in a high-demand national newspaper. Wedding etiquette expert Peggy Post advises submitting your announcement as soon as possible. You'll have a better chance of getting it published if you send it in sooner, since most newspapers receive more submissions than they can print.
Typically, you'll be able to submit your announcement via e-mail or snail mail. Just check with the paper to see which method the editors prefer. If you're planning on sending a picture, some papers won't return it (even if you send a stamped and self-addressed envelope), so you may want to send a copy instead of the original.
Usually, announcements are published the day after the wedding. If you want to include a picture of you and your groom on your wedding day, the newspaper can run the announcement a few weeks after the big day.