How do I fix a running toilet? my boyfriend's toilet always runs& we usually only tap the touch or...

my boyfriend's toilet always runs& we usually only tap the touch or play w/it til it stops. How do we fix it permanently so it doesn't run anymore? Thanks
Answers:    replace the flapper first ,,,, its any staying up or not seating in good health, thats why jiggling manipulate works

this wastes a tremendous amount of hose
uh call a plumber.