considerDon't make any decisions before you've considered the matter.
ponderformalShe sat back for a minute to ponder her next move in the game.
mull overI need a few days to mull things over before I decide.
reflectformalI spent a lot of time reflecting on what he'd said.
agonizeShe agonized for days before agreeing to take the job.
agonize over/aboutHe agonized over his poor choice of words earlier.
broodShe sat brooding in her room for days after she and Gary split up.
dwell onThere's no point in dwelling on the past.
rack your brainsUKI've been racking my brains all day but I can't remember where I put my keys.
rethinkHer family's disapproval made her rethink her plans.
reconsiderHe was reconsidering whether to accept or not.