In the approval process, when user submit for approval, system will send an email to approver using email template defined in Approval Assignment Email Template, but this template is not mandatory, so when no template defined, system will use default template with a link to Approval Page Layout page in system.
When using custom email template for approval submission, use following merge field to bring approver directly to the approval page layout: {!ApprovalRequest.Internal_URL}
Sample email template:
Dear Sir or Madam,
{!User.Full_Name__c} ({!ApprovalRequest.Process_Assignee}) has requested your approval for expense with amount: {!NullValue(Expense__c.Amount__c, "0")}
Expense detail: {!Expense__c.Link}
Expense status: {!ApprovalRequest.Status}
Please click this link to approve or reject {!ApprovalRequest.Internal_URL}
regards,
Salesforce.com
** notice the usage of formula {!NullValue(field name, string)}
There are few ways for approver to approve or reject the approval process request:
1. Record page layout - Approval History
Scroll down to Approval History related list of the record page layout, just make sure Approval History is added to the page layout. All users (with access to the record) will see the approval history here, from when and who submit for approval, when and who approve, how many level of approval and reassign history.
2. Home page - Items to Approve
Home page is the landing page when user login to Salesforce, so it is good idea to add Items to Approve component in the Home Page Layout. Only items need to approve by that user will show in user home page. User can approve or reject from here, or by click a link to open record detail. It also show who and when submit for approval.
3. Chatter page
To enable approval process in Chatter, navigate to Setup | Customize | Chatter | Settings, looks for Allow Approvals and enable it. Once enabled, all approval process will be available in Chatter.
If the approver have Salesforce1 mobile app, he/she will see the approval request as notification in the Salesforce1 app. Click the notification will allow user to approve or reject from the mobile.
4. Email
When enabling email approval, system will lets users to reply to email approval requests by typing APPROVE or REJECT in the first line and adding comments in the second line.
To enable approval from email, navigate to Setup | Create | Workflow & Approvals | Settings, look for Enable Email Approval Response and enable it.
If there is no template assigned to 'Approval Assignment Email Template', and approval via Chatter is enabled, screenshot below taken from email received by approver, where user can use acceptable words: APPROVE, APPROVED, YES, REJECT, REJECTED, NO - not case sensitive, to approve or reject.