“Oops, I forgot the attachment in my previous email. Here it is” — I’m sure you would’ve either sent an email with this message to somebody  (or) received an email with this message from somebody.  When you are sending emails in a hurry you may forget to send attachments. It will look unprofessional when you are sending a very important business related email and forgot the attachment.
The cure is Gmail’s Attach Alerter. If you have the word ‘attach’ in the mail content, and did not attach anything, you will be alerted by Gmail before sending that email.  To enable this feature, do the following.
Fig: Attachment Reminder
Fig: Gmail Attachment Reminder
  • Click on “Settings” link,
  • Click on “Labs” tab,
  • Select “Enable” option button in “Forgotten Attachment Detector”
  • Click on “Save Changes” at the bottom
This will help your message recipient not to receive inevitable follow-up emails with attachments.

Attachment Tip: Attach before composing

It is good idea to attach the file before start typing the message. This way Gmail will be uploading the file when you are typing the email.  When you are done with your email typing, the attachment is already uploaded and you can send the email immediately.
You can delete an attachment by deselecting the check box in front of the file name.

Attachment Tip: Attaching multiple file names

You can attach multiple files in Gmail by selecting the multiple files in your file browser by holding shift or control key for contiguous or different files.