Best game design and development approach

Hi to all,

i would like to have your opinion on designing and developing games which is the best practice?

Assuming that we have the concept and the idea of the game which is best :

1. Design the Game Levels and then add the logic i.e collisions , triggers, moving objects, animations e.t.c

2. or start building everything bit by bit meaning make a scsne apply or the logic continue to other scenery e.t.c?

thanks in advance