It is so important for you to set up your recruiting system properly whether you are a external head hunter or a manager setting up your recruiting department. It is important you do everything you can to get to candidates and retain them well as they go through their job decision process.
If you are not getting to candidates until a couples weeks after they have shown some level of interest then you are too late or they are probably not an ideal candidate. The best candidates you have to get to on day one before your competition does.
Candidates will start off looking for opportunities online at career pages, niche sites, forums, etc. before talking to any trusted source. This is when you can first find them. After this they will start talking with peers they have worked with before or recruiters they have had good experiences with.
They are not willing to leave their job, but they are losing interest in their current position and realizing they are not happy with their future. They are looking for jobs that will stretch them with exciting work and innovative projects.
In fact a candidate will go for less pay if they can see there is a great future in a new career where they feel valued and that they are doing something exciting. It just has to fit where they see themselves going in life.
If you are trying to find a candidate for a specific company than you need to know who that ideal person is for that company. Know what they want and make it exciting in your online advertisements toward your candidates.
Look for ways to leverage with SEM and SEO to get your brand out there faster with more eyes able to see it. I suggest that you go toward EnticeLabs and TalentSeekr if you want to focus on SEM and Jobs2Web if you are targeting SEO.
As you find these solid candidates you have to create solid recruiting nurturing tanks. The best way to do this is with a solid recruiting CRM like iCIMS to collect these names and keep marketing to them while saving you time.