To fly with passengers you must have completed 3 landings within the preceeding 90 days. If taking pax at night, one of the 3 landings must have been at night - that's called "keeping current".
If hiring club aircraft, many clubs insist that you have flown previously within the last 30 days.
As far as renewing your JAA PPL(A) licence is concerned, you must, in the 2nd year of your licence, complete 12 hours as Pilot in command one of which must have been with an instructor.
See Lasors 2007 (search Google for the pdf).
(I think!
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Note that although going up and doing 3 circuits every 3 months, while it does satisfy the currency requirements for pax, probably won't do your flying any good!