Considering my own personal experience, and personal choice to always level cooking, in every MMO i play i figured i'd offer some advice of my attitude towards this topic, it is one thats quite close to my heart 
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Though IRL i'm an abysmal cook, i get by on the most basic meals if i'm cooking for myself, (A lot of ready meals, or packet meals, or take it out of the freezer and whack it in the oven meals) I do have a love of cooking, i watch loads of TV shows about it, i once dated a chef, i've read recipie books and have a few (specificially cake ones) even though i've never tried to make them.
What i've always found when RP'ing a craftsperson, is to always be enthusiastic about your craft, even if you lack knowledge about that certain craft or its components, enthusiasm wins out.
I suppose another factor to keep in mind is how much of a busy body you want your craftsman to be, i like mine to be busy, chatty, and generally active which is why i plug for enthusiasm, if however you'd rather a quietly confident artisan, one who knows their own skill limits but doesn't give away their secrets, or their inner-joy at making things anew, then theres a lot of RP potential there too, to quote a famous movie :
"When Pope Benedict asked Giotto for a drawing to prove his worth as an artist,
Giotto drew a perfect circle - freehand ... perfection is a powerful message".
.Though IRL i'm an abysmal cook, i get by on the most basic meals if i'm cooking for myself, (A lot of ready meals, or packet meals, or take it out of the freezer and whack it in the oven meals) I do have a love of cooking, i watch loads of TV shows about it, i once dated a chef, i've read recipie books and have a few (specificially cake ones) even though i've never tried to make them.
What i've always found when RP'ing a craftsperson, is to always be enthusiastic about your craft, even if you lack knowledge about that certain craft or its components, enthusiasm wins out.
I suppose another factor to keep in mind is how much of a busy body you want your craftsman to be, i like mine to be busy, chatty, and generally active which is why i plug for enthusiasm, if however you'd rather a quietly confident artisan, one who knows their own skill limits but doesn't give away their secrets, or their inner-joy at making things anew, then theres a lot of RP potential there too, to quote a famous movie :
"When Pope Benedict asked Giotto for a drawing to prove his worth as an artist,
Giotto drew a perfect circle - freehand ... perfection is a powerful message".
