How do I choose between different staffing firms for testing candidates before a full-time hire?

When comparing staffing firms for testing candidates before a full-time hire, focus less on “who has the biggest pool” and more on who can reliably deliver the kind of candidate evidence you need to make a safe hire.

1) Start with your hiring goal

Ask:

• Are you trying to reduce bad hires?
• Validate technical skills?
• Check culture/communication fit?
• Fill roles quickly with a temp-to-perm path?

Different firms are better at different things. A firm that’s great for high-volume admin staffing may be weak at pre-hire technical screening, and vice versa.

2) Compare their candidate screening process

This is the biggest differentiator. Ask each firm:

• How do you screen candidates before submitting them?
• Do you use skills tests, work samples, technical interviews, or reference checks?
• Can they tailor screening to your role?
• Do they verify employment, credentials, and background?
• How do they assess soft skills and reliability?

A strong firm should be able to explain a repeatable process, not just say “we interview everyone.”

3) Ask about the trial-to-hire structure

If you want to “test” someone before a full-time hire, understand the model:

• Temp-to-perm: candidate starts as a contractor/temp, then converts
• Contract-to-hire: common for validating performance over weeks/months
• Direct hire with probationary period: less common via staffing firms

Clarify:

• How long is the trial period?
• What fees apply if you hire the candidate permanently?
• Are there conversion timelines or penalties?

4) Evaluate their specialization

Choose a firm that understands your role type:

• Tech staffing for software/IT
• Finance/accounting staffing
• Industrial/light manufacturing
• Administrative/customer support
• Executive search

Specialized firms usually have better screening criteria and a stronger sense of what “good” looks like in that job family.

5) Review candidate quality, not just quantity

Ask for proof:

• Fill rate
• Time-to-submit
• Time-to-fill
• Offer acceptance rate
• Conversion rate from temp-to-hire
• Retention after 90 days or 6 months

High-quality firms can show that their candidates stay and perform, not just that they can send resumes quickly.

6) Check their recruiting and account management responsiveness

You want a firm that:

• Responds quickly
• Understands your feedback
• Adjusts candidate profiles after misses
• Gives honest advice if your requirements are unrealistic

A good recruiter becomes a partner. A weak one keeps sending mismatched candidates.

7) Understand cost structure

Compare:

• Markup or hourly bill rate
• Conversion fee if you hire the candidate directly
• Replacement guarantee
• Minimum hours or commitments
• Background check/testing add-on costs

Don’t just pick the lowest rate. A cheaper firm that gives weak candidates usually costs more in manager time and turnover.

8) Ask for references and relevant case studies

Request:

• Client references from similar companies or roles
• Examples of how they staffed a similar position
• Their success rates for contract-to-hire placements

If they can’t show relevant history, proceed cautiously.

9) Verify compliance and risk management

Especially for trial hires, confirm they handle:

• Payroll and tax compliance
• Workers’ compensation
• Background checks
• Drug screening if needed
• Labor law / co-employment issues

This matters more if the candidate is working through the staffing firm before conversion.

10) Run a pilot before committing

If possible:

• Give 1–2 roles to each finalist firm
• Compare candidate quality, speed, and communication
• Track conversion performance over 60–90 days

A small pilot often reveals more than a sales pitch.

Simple shortlist criteria

A good firm should score well on:

• Role specialization
• Screening rigor
• Candidate quality
• Temp-to-perm terms
• Compliance
• Responsiveness
• Conversion and retention outcomes
• Transparent pricing

Questions to ask each staffing firm

1. How do you screen candidates for this role?
2. What percentage of your submitted candidates get interviews/offers?
3. What is your temp-to-perm conversion rate?
4. What is your fee if we hire the candidate full-time?
5. What happens if the candidate doesn’t work out?
6. Can you share references from similar placements?
7. How do you handle background checks and compliance?
8. How quickly can you provide the first qualified candidate?

If you want, I can also give you a comparison scorecard template you can use to evaluate staffing firms side by side.