I played in a club game sunday  with a novice and bidding was:

 

1nt x p   and I with my 3  points "pulled it to 2 spades.

We were vul  and she having  2 spades went to 2nt    

Anyway I was told I should not have  bid since we were vul and  we have to much to lose  - 200  -300  etc as oppose to maybe  180   or  280 etc 

 I never think of this at the table..  first of all  I have never learned the  scores

and I  go on automatic  and bid what I think I am SUPPOSE to do. 

I now am studying the scores  and hopefully will know the cost and can use  some judgemnt instead of going on autopilot  next time.