You may be an engineering firm that sources your leads from two areas.  One is government for large infrastructure projects and the other is the private sector.  The former may require more emphasis on high quality proposals to win jobs and the latter will rely on relationships in addition to high quality proposals.

Your firm records all potential projects coming up over the next 5-10 years, in a pursuit file. You have sourced this from various registers and contacts. This list of potential projects helps your business development team coordinate its activities and plan resources with project teams throughout the company.  This coordination and planning allows proposals to be prepared accurately and in a timely manner and to be adequately resourced should you win it.

Lets assume you are an approved organisation on the government register and therefore able to tender proposals for government jobs.  You have created awareness and interest in your organisation by going through this approval process.  Likewise you have met senior managers of developers and established good working relationships.  Both of these take time but are all part of the sales and marketing process for generating new and repeat business.

At this stage you have not yet moved your client from interest to enquiry. It is the enquiry stage that helps determines if a lead is "qualified" or not. 

Now there may be several steps within an enquiry stage and it is important to define what these are. For an engineering firm this might be a developer's request to tender is received on your desk. You are given 10 weeks to submit your proposal.  The developer makes a decision within 2 months and you are successful!

The client action of delivering you a request for tender is a "qualified" lead and can be closely measured against your sales and marketing activities required to get your client enquiry to a purchase. This proximity allows for more accurate indication on how well your sales & development team has been able to convert when it counts. Being able to link the expenses associated with producing a proposal (Business generated) and managing relationships (Self generated) during that process, with winning a contract, provides what we call a "lead cost of acquisition".

It is important to have a clear policy around when a lead is a qualified lead.  All staff then has a common understanding of terminology and what they need to do to reach targets.