JoannesPaulus: Yeah, it is a famous book , may be a bit too much info.
oermens: Yeah, I have done that already, I am just looking for a short list of dos and don'ts, may be a tutorial of how to draw layout in cadence.
If you have never done layout before, you should learn the basic techniques of matching, drawing busses and so on... you do not need to read the full book just the important chapters...
About the symmetry, I can understand that the two inputs should basically "see" the same transistors and all, but what if you have several blocks? Is it enough to make each block symmetrical? Or should the whole thing also be symmetrical?