I've had credit cards since my teen years. They provide purchase protection, they make it easy to pay for things, they give rewards, and I've never paid a penny in interest.
I still feel as if I'm new to adulting, for example, I'm 30 years old and have never had a credit card. I'm looking into one now, for frequent flyer miles, but I have no idea what I'm really doing as I'm researching all the different options. I want to make an informed decision before I sign my life away, what are the things I should be looking for/looking out for?
-For you, probably avoid a card with an annual fee. Not all credit cards with annual fees are bad for all people (I have one and it makes sense for my situation due to the benefits it provides), but as a first/only credit card, you'd almost certainly want to stick with one that has no fee.
-Look for a card that gives higher reward percentages for things you personally buy a lot. A cool example is the Chase Freedom card; you get 1% back on everything and then there are rotating categories that last 3 months each where you get 5% cash back on certain things like groceries, Amazon, gas stations, and certain major stores. Other decent cards can give 1.5% back on everything, period. Spend a bit of time comparing rewards to see what card matches your spending profile the best. It's probably not worth it to go overboard on searching though; if you put $12k/year on your credit card ($1k/month), and get a solid 2% back, that's still only $240 a year. Plus if you find a better one later, it's not a big deal to get another card, within reason.
-Visa and Mastercard are more widely accepted than Amex and Discover because they have lower merchant fees.
-Interest rates aren't the important variable to compare between cards if you are sure you will be paying off the debt every single month, as anyone should be doing. If you don't plan to pay it off every single month without fail, don't get one.
-Check your credit history before applying to make sure you don't have anything that would push down your credit score a lot.
-A low credit limit is usually given for people without much credit history. One thing to look out for is to keep your credit utilization low. If you have a card with a $1,500 limit, then constantly putting $1,200 on it each month doesn't look great even if you pay it off. That would be 80% credit utilization. It shows that you're using most of your available credit. It's best to keep credit utilization fairly low if you want to optimize your score, either by using it little or by eventually getting a higher limit. My credit utilization on my main card is under 10% and my credit utilization when all my cards are considered together, is less than 5%. It doesn't need to be that low, but the lower the better.
I think this point gets oversold. If you have a student loan, you have a credit history.
Credit mix is a variable too, though, when it comes to optimizing a credit score. Having installment credit (like a student loan or a mortgage) as well as a revolving credit (like a credit card) gives a slight advantage compared to having just one type of credit.
Length of credit history matters too. Student loans eventually get paid off. But having a permanent credit card account that can eventually last decades, can stay around as long as you want and builds a really long continuous credit history.