I am sure this question comes up dozens of times a week! It's a perennial favourite, and we constantly re-invent the wheel. As I have commented in the past, here are my thoughts yet again.
Firstly, I would suggest that you need to look at your Recruitment and Selection process. If I understand the underlying message in your posting, you do not appear to have a robust recruitment process in place to ensure you get the right candidates.
Secondly, from my reading of CiteHR over the last umpteen years, almost everyone seems to work on some sort of hit or miss type of scheme. Round up a thousand people looking for a job, interview them, and hope to God you find someone remotely suitable! And then you wonder why you can't get the right person. That is not recruitment.
Here again is Aussiejohn's 6 Easy Steps to Recruitment and Selection.
If you want the right candidate for the job, you only need 6 things:
1. A proper position description which sets out the requirements of the job
2. A person specification setting out what the successful candidate needs to perform the job
3. A rigorous selection process based on the PD and PS, to choose the top 4 candidates to interview
4. A targeted interview questionnaire based on the PD and PS, to ensure the candidates can do the job and can integrate into the company - no stupid, irrelevant questions that have nothing to do with the job
5. Well trained interviewer/s
6. A rigorous reference checking process
Place well worded advertisements, or work with a trusted employment agency who will source the RIGHT type of candidates for interview.
That's all there is to it. No need to complicate the process. Remember the KISS principle.
MAKE NO MISTAKE. THIS WORKS. I have used this process many times in companies I have worked for, and I have also trained other people to implement the process.