Whatever works best for you. Though, having done this before, you'll probably find that a paper clip is not the best material for a pick. The ones that are sturdy enough to hold their shape won't fit well into most keyways, and the ones that fit usually aren't sturdy enough to hold up to use as a pick. You'll likely have better luck using something flat and thin.
It's not being used for anything. But sometimes I practice with a 1 pin lock. Sometimes I practice with a 2 pin lock. Sometimes i practice with a 3 pin lock. The pins have different sizes. So I practice with different arrangements of pins. For example short pins in front and long pins in back or long pins in front and short pins in back. Some arrangements of pins are easy and some arrangements of pins are very hard. For example if I put 1 long pin in front and a slightly shorter pin behind the long pin, that arrangement is easy to pick. But if I put the long pin in front and a much shorter pin behind the long pin, that arrangement is too hard. How do i make sure i can pick that arrangement, that consist of 2 pins and the long pin in front and the much shorter pin behind the long pin?
The answer to that question is not as easy as you might think. Some people prefer certain height of the hook, some prefer taller or shorter hooks. Some prefer a very slight bend in the hook, some prefer a much steeper bend. What works well for one picker may not work as well for another picker. And a pick that you can’t seem to open anything with someone else may seem able to open many locks.
You should try making a variety of picks, and see what works best for YOU.
Gordon
Just when you finally think you have learned it all, that is when you learn that you don't know anything yet.