We ourselves do not analyze PET data very much anymore, so some of the analysis protocols in these pages are quite out of date, referring to SPM96 and SPM99. Having said that, the SPM interface has not changed very much since then, so you may well be able to work out the corresponding steps in the more modern SPM versions.
PetHeadcurves - using the PET bolus time to optimize your study
PetPreprocessing - old preprocessing page for SPM96
PetStatistics - for SPM99
PetAnalysisProtocol - SPM96, ditto
For more general principles, see also:
Let's play PET - an introduction to Positron Emission Tomography from UCLA.