Loaded question.  There's no such thing as the perfect candidate.

There is, however, the candidate who you want REALLY bad.  They've got the skills, and you don't want to beat around the bush and risk losing them - you feel like you might be in a competitive situation, against others or against a counter-offer from their current company.

So you've got to make the first offer count.  How far do you go?

--5%?  Only if you're looking to get in a bidding war or perhaps have the candidate drop you without countering and say, "You know, I've decided that I'm OK where I'm at"

--10%? The standard from which all offers are measured.  A 5% raise is a paltry merit raise to most high performers, but 10% becomes something to consider.  Most candidates will evaluate the offer including a 10% raise, but high performers will negotiate and perhaps drop you like the average candidate would if you offer 5%.

--20%?  Now you're talking.  20% is gold standard when it comes to the pay bump you're giving a star candidate.  That's the threshold that it takes to get the attention of a player, and the 20% bump has the added attraction of going beyond what a bureaucratic company can do related to a counter.

The other thing that's interesting about the psychology of the pay bump included in the offer is that it's relative to the engagement of the candidate.  The numbers we provided above are an opinion of what it would take to rip a high performer with average engagement levels from a competitor. However, if the engagement levels of the star performer are low or she's otherwise disenchanted with the company, you can move from 20% to 15%, even 10% related to your offer to the star.

Which means you have to read the tea leaves.  Someone you consider a star that was a direct apply to your website has some engagement issues.  Don't start at 20%.

Passive candidate you consider a star?  Think long and hard before you offer 5% or even 10%.  Going to take more.

Happy hunting.