When it comes to choosing a web designer, you need to establish what is important to your business. If you are very much driven by price and have a strict budget then you will need to find a web developer that can build you your site for the money that you have allowed. It may be that money is not really the main issue as long as you get all the functionality you need and the site is finished to a high standard and within a time limit.
Firstly you need to decide exactly what you want your website to do, you can always play around with the way it looks, but knowing what functionality you need is essential. Once you have this you can start to obtain quotes for the site. You may find that some developers will only programmer the site and will not design it, and vice versa. Ideally you want to use a company or individual that can offer both otherwise you may have issues with communication between the two.
If you are driven by price, be careful of going for a quote that seems far too cheap as you may end up being disappointed with the results.