Say a consulting firm (such as mine) offers services to help businesses with their social media strategy, digital PR and personal branding but receives random requests for SEO advice or help in setting up and managing a Facebook page.

Instead of just dismissing such inquiries, embrace the person's business problem and offer a partial solution based on how your consulting firm can help. Still have a conversation and offer some services; they might not be a complete answer but can work as part of a more sophisticated and integrated approach.