What Rick didn't mention, and has beaten into my head, is that the first bass note in the pattern should virtually always be the root note of the chord (that is why you hit the 5th string first for the C and the 4th first for the D7 and so on) while the second alternative plucked is usually the 3rd or the 5th. This gives you an anchor when you start mucking around with bass runs (going from the root note of one chord to the root of another, like going from a C bass note to a G by working back down from a B, A, to G, or vice versa.). If you don't get "rock solid" on which bass note is the starter (as herr Rick says), then everything turns into mush later on when you start playing around. Right, teach?
yours, Peter T.