Best in terms of efficiency for you or best in terms of business ethics?
Unfortunately, it seems the only good way from an efficiency standpoint is to steal them from competitors!
Ethically you could recruit at job fairs and websites like Monster.com, AutomationTechies.com or other similar. But realistically that has not worked well for me. Last year I posted an opening on Monster for a drive and soft starter technician and got over 2700 responses, of which only 15 had any direct experience with drives or motor control, and NONE of them wanted to travel. They were mostly propeller-heads looking to get out of the now non-lucrative "high-tech" bit tweaker marketplace.
The military is OK as long as you are willing to "deprogram" them from thinking that whatever branch they were in had all the right answers and there is no questioning that fact. Their experience is less direct as to drives and PLCs, but they are usually fast learners and already understand how to think on their feet, a great quality in the field. We got a great guy from the Navy, but for the longest time we had trouble with his understanding of the concept of "grounding".
"Venditori de oleum-vipera non vigere excordis populi"