Trial jobs happen at the point that you would be ready to hire that candidate. This is after you have evaluated if they are excitable if they fit well in the current culture of your company or would bring a good change to your company culture, and if they have some level of technical expertise (they went to college, worked at another development position, or have side projects).

Trial jobs would be ok for some candidates, but I would be furious if, after spending a lot of time in the interview process, a company tells me only at the end that the job is a contract to hire job. Trial jobs should be advertised up front at the start of the process.

Well of course, I was more just asking what his ideal process is to funnel out candidates up til that point. Whiteboard interviews? Take home interviews? What's your strategy?