The opening minutes usually carry the day's fastest moves and the least preparation. A routine moves the thinking earlier, when nothing is at stake.
A workable one covers three things: the market - key levels, scheduled events, overnight range; the plan - which setups qualify today, at what size, with what daily limit; and the person - sleep, stress, whether you are in any state that historically precedes bad decisions. The last one is the one people skip and the most predictive.
Keep it the same every day and keep it short. The value is in the invariance, not the content; a routine that changes with your mood is just another decision.
Related: checklist-discipline, trading-plan, sleep-debt, daily-loss-limit