Sometimes you can get the wrong impression (like feeling they're pulling one over on you). But the most direct thing to do is ASK them what their experience is.
I've worked in bike shops for a few years now, and for the most part I've seen that mechanics really want to do a good job. There's an old saying that basically says "the first bike is sold by the salesman, the rest are sold by service".
Trust your instincts, and ask when in doubt. Watch out for up-sells. They should want to fix what needs fixing, inform you of anything else wrong that they find, be open, and do the job right. If something goes wrong, they will fix it.
Good luck. If things don't work out, be patient but don't give up- it's on them to do the job right. On the other hand, make sure you realize that you get what you pay for.
If you have any specific reason you feel uneasy, post it. Otherwise, maybe you need to get in touch with some people in your local moto community about the shop in question. As far as resources go, check the FAQ here and check out the...internet!
seeya,
Scott.