Link to Shopping Networks for Points and Cash Back
There are several card linked rewards programs. If you shop at a store/restaurant/establishment in the network, you get a percentage of your purchase back in miles/points/cash. Some of these rewards networks are mutually exclusive in that you can't enroll in some of them simultaneously. Most notably, you cannot enroll the same card in multiple airline networks (despite this, it is a fantastic way to keep your airline miles alive). Doctor of Credit has a fantastic list of these rewards networks.
Set Up Autopay
Even if you're not a fan of autopay and would rather make manual payments, I still highly recommend you set it up as a failsafe: every bank I've dealt with (and I have credit cards from 12 different banks) has "smart" autopay in that if you've made a partial payment during the month, the autopay amount only pays the amount remaining. And if you've made payments in full, the autopay just doesn't pay anything. They don't just blindly pay the last statement balance without taking into account previous payments you've made during the month. So even if you are diligent in making manual payments, autopay can kick in if you ever forget.
Set Up Transaction Alerts
Some people log into their accounts regularly to check for unauthorized charges. This is far too much effort for me; instead I set up email alerts for any transaction on the card (most banks will only let you set alerts for charges of at least $1, with Amex being an exception at $10). Most banks will support text messages for this as well, but I just prefer email.
Set Up Electronic Statements
Saves paper and reduces the risk of having my account compromised by my statement being intercepted in the mail (Chase has your full credit card number on the statement. And obviously your billing address).
Set Up Reminders to Cancel the Card and Use Benefits
This delves into the world of travel hacking and credit card rewards, which I cannot possibly explain in its entirety in this short post. But in short, most cards I sign up for are for the signup bonus: this typically entails spending $1000-$3000 in the first 3 months and earning a large sum of points or cash. Typically these cards have an annual fee, and most cards are not worth this annual fee after the first year. Hence, I add a task to Taskwarrior (though my to do list app recommendation to people not comfortable with command line programs is Todoist) with a reminder to cancel the card before the second annual fee.
Furthermore, I add a task to use up any credits - such as the $300 travel credit from the Chase Sapphire Reserve.
And finally, I add a task to make sure to spend enough to meet the signup bonus.