the easiest fashion of potentiating your opiates is through time potentiation with antacids, this of course only works with oral users. you can easily squeeze another 4 hours of high out of 2 medium strength tums taken with your dose.
now a more tricky potentiation is with grapefruit juice. you should only take about 2/3rds of your average dose when you do this. drink the juice one full half hour prior to dosing, then eat some antacids to nuetralize the citric acid's raising of your stomach PH. this affects both the time and intensity of the experience. particularly with dihydromorphinones.