This is a mistake that many people make and it does make the overall search harder, it is important to decide exactly what a property needs to have and when you start searching, may not prove to be a necessity.
It does save a lot of time and can result in you losing out on a dream home by not setting out exactly what you need so make a list from the start of what is essential and narrow down any suitable properties in the selected town from there. You will be amazed what a difference it can make.
Top Tip: If you are unsure what to search for in a property then I would suggest buying a property that has some form of off road parking, with a garage would be great and most definitely a garden. This combined with excellent transport links and local facilities can work wonders, if you decided to later sell and move on then this will shift the property a lot quicker.