Well, I can think of at least a dosen of ways to do that - you will have to be more explicit if you want an answer.
Depending on the MCU you have, you could use the ADC in continuous conversion mode, where the ADC scans multiple channels and the DMA transfers automatically the results into SRAM. Than, in the DMA interrupt you can process your results. This is a very efficient solution, and a great thing on an 8-bit MCU.
Reading and understanding the Reference Manual would be the best thing for you to do, like this you get a good idea of what you could do and how.