I remember in college that we were told to not sign the signature strip on the back of the card, but instead to write "SEE ID", meaning see the signature on our driver's license. Is this a valid security practice that I should still be doing?
Writing "see ID" on the back isn't a good practice nor recommended by any credit card company. The space for a signature on the back is for you to sign that you agree with the credit card company that you authorize the purchases and will pay back debts incurred by the card, not to allow the merchant to use as a reference for your signature. Technically if you don't sign it (e.g., if you write "see ID"), your card isn't valid and the merchant could refuse to accept it at all, with or without ID.
Even if comparing signatures was the purpose of that space, as a practical matter either it would be useless. Our signatures on those electronic things or on receipts generally look nothing like whatever is scribbled on our cards. No one ever compares signatures to what's on the card. They also don't read whatever you have written instead of a signature.
My wife has always written "see ID" on her cards and doesn't care that it's wrong on every level. Clerks never ask for her ID. In fact, I believe they are not supposed to.
The goal is to ask folks to validate your identity using something a bit harder to forge than a signature. Driver's licenses and other government-issued ID often carry a photo and have anti-forgery measures designed into them, and the potential legal consequences of forging one of those (if anyone goes to the trouble) may be more severe than for simply forging a signature.
But many stores ignore this request; many, in fact, don't bother checking the signature at all. So it isn't at all clear this actually decreases the risk of a stolen card being used. And the protections on credit cards limit how much the cardholder is liable for, so outside of the annoyance factor the risk is really to the store more than to the cardholder.
It's a reasonable idea, it just doesn't work as well as expected.