For an elliptic gmC filter where pole Q is normally quite high you will be more prone to layout parasitics fouling up your reponse/gain. So pay attention to parasitic R (short tracks not too narrow, ensure good via coverage where needed) as well as C (use higher level metals) and an post layout extracted simulation is a must to check the performance.
Also be aware non-schematic items like antenna diodes which may not be extracted from the layout.

I guess its differential so of course pay attention to symmetry. Anyway try the excellent book by Alan Hastings "The Art of Analog Layout".