op, the two guys above me hint at the good point that if you have any apprehension, it might be worth verifying your work with a torque wrench and a spec sheet. most manufacturers publish a recommended torque on their websites, and it never hurts to be safe.

the suggestion that not using a torque wrench, especially on durable mid-range parts, will result in said parts falling off your bike is clearly alarmist bull**** (but you know that, right?). most people, professional mechanics included, who adjust the stems, seatposts, wheels etc. on a bike do so without using a torque wrench most of the time. common sense is key, and our senses can always be refined.

if you want an idea about when to use a torque wrench, do a search. this question has been asked in the mechanics forum before and they've got a more sensible range of opinions than you're going to get around here.