Patch inclusions

I just have a general question regarding patch inclusions. When a patch is submitted is there a formal review and testing of the patch prior to inclusion? From what I have been following from this list is that the process is patches get applied to new/existing bug/feature requests, bug fixes are priority numero uno, test cases should accompany new functions then testing? How likely are patches which may receive low usage from developers still applied? Also, besides the usual retrieving latest testing branch, compiling running tests etc. how else can one help? -- Jas