Timing and frequency are crucial factors to consider when sending push notifications. You don't want to send too many notifications and risk annoying your audience, but you also don't want to send too few and risk being forgotten. One best practice is to only send notifications when there is relevant and valuable information to share. Also, be mindful of your audience's time zone and schedule your notifications accordingly. According to a survey by Leanplum, the best time to send push notifications is between 10 am and 1 pm.