I guess you can start off by finding your information here
Something will happen and you will learn more than you wanted to know.
In the mean time, know as much about you system(s) as you can.
If you want to be a certified iSeries admin IBM only has one course currently, the 976 test for 6.1 admin certification. At this point it doesnt look like they will be making a 7.1 test, as 7.1 has been out a while and still no test…