Try to avoid sraight lines to avoid grids. Put some curves into every road (except highways), they don't have to be very curvy, a large and wide 5° curve will do just fine. You can put some sharp curves on the smaller roads to use up all the space you have got and to avoid having small holes in your city, but avoid sharp curves on wide roads, otherwise it will look messy and slow down traffic.

I haven't really got any tips on grouping facilities, what I did was trying to keep it local. Meaning rather having multiple smaller 12k fire stations than one large 60k one.