Defineately get someone experienced to teach / show you, once you've got the hang of it, it's easy but like everyones said previously take care and be really gentle as it would be very easy to cause damage.
I read pilbara's advise on his web site about doing it by viewing tail area and it works too, very interesting, though i do confirm that tecnique by probing to be 100% but so far can't fault it either.
There wil be someone in the herp world who'll be happy to show you. It's all about learning, though i never probe hatchies or really small snakes but that's just me until there atleast 6 months old, each to there own.....