[Bug-tar] question about tar command

[Hien Huynh]

Dear Sir,
 I'm a student at VietNam. I'm studing about back up data. But I don't
know how can I use "tar command" to backup new files by incremental backup
method ?
 Please tell me the full command of tar , and the position of operation
modifier " -G , -g"... It's better for me if you give an example.
 Thank for your helps
 Best regards
 Huuhien
 HCM city , VIet Nam