No matter what kind of device or operating system you use -- Android, iOS, BlackBerry, Windows, Mac OS X or Unix -- you should be using a password manager. These apps help you generate and store complex passwords. They also help you remember credit card numbers and other sensitive information while on the go.
For best results, find one company that makes a password app for every type of device you own, including your Web browser, and that synchronizes data across those devices. Ideally, the password software will use a strong encryption algorithm, although that's harder to verify.