Before you begin looking for a new PDA or smartphone, it is a good idea to make a comprehensive list of all the features you want, and come up with a target price range (what you are willing to spend).
One of the most important features to consider in any PDA is its storage space. If you plan to use the device for storing multimedia files such as pictures, videos, or flash movies, this figure is absolutely integral, but even users that are simply looking to save and store documents should take this into consideration.
Processing power and RAM are also important if you intend to run memory-intensive applications, such as photo editors and 3D games. If you are only looking to use the device for word processing and email, however, these features will not be so much of an issue, but they are still worth looking at for comparative purposes.
In this day and age, one feature that nearly every PDA user will want is some sort of wireless internet access. Whether it be built-in Wi-Fi, or a more mobile option like cellular broadband, it is important that your device gives you the freedom to access email and the internet without having to connect to a laptop or external modem.
Once you have established a list of PDAs that have all the features you're looking for, it's a good idea to do some detailed price comparison, and decide which devices offer the best value for money. The main purpose of this step is to avoid paying for extra features that you do not want or need, and to determine which device best meets your specific criteria.