1. Read Books: Analog Integrated Circuits Design by David & Martin.Get fundamental understanding of ADC.
2. Select ADC type, and find some papers on IEEE JSSC to try reference design.
System level simulation using Simulink or Verilog-A is necessary.
u can start of by going through CMOS data Converters for communications.....but if u can actually decide on the specs of ADC then the first step would be to narrow down to a specific architecture....