i usually go to places family recommends. DH's best friend's dad is a jeweller in Toronto and my ring is from him and he has also made me a few other pieces. i also buy things when i travel and u can always google a jeweler, put a request on here for recommendations and also u get a sense of the place when u go in. how organized it looks, other cliens, location, etc. in NYC i go to the diamond district and i looked up vendor websites first. also chekc for accridations on the site- bbb, jeweler associations etc.
i go to trusted jewelers for new pieces, apraisals, and havig things sized. when in doubt i look for a big name- ie birks always does my apraisals.