Most of the password management apps have this built-in, but you can also find standalone password generator apps for your phone. You want to use long passwords with every kind of acceptable character. So you want a password that looks like 6+d5EJEPH8Wu-A*RE4r2!e_r rather than 1l0v3myp@$$w0rd. Sadly, you will find that many sites will require you to limit the special characters or the number of characters, which means that not all the sites that you trust with your personal information are using the best security practices.