When are lead assignment rules triggered in Salesforce?

Hi,

Some scenarios are given below :

1.  Creating a Lead Manually : Make sure you have checked the checkbox "Assign the active assignment rules" in optional section.
2. Web to Lead : Lead will be generated and at the same time assignment rule will be triggered.
3. Salesforce processes any rules in the following order:

• Validation rules
• Assignment rules
• Auto-response rules
• Workflow rules (with immediate actions)
• Escalation rules

Workflow field updates that run based on an approval process or time-dependent action do not trigger any rules.

Thanks.