First of all you have to know what functions (javascripts, mysql databases) and design languages (html or php)would you like to use in your website. Next, you would want to figure out the specific purpose of your website. Will it be a website to display a company's services or would it be an e office type website (wherein files can be uploaded and messages exchanged)?
In finding affordable web designers try to scout the net for websites which purpose is the same as yours. Usually they will have a 'site designed by' credit at the bottom of their website. If not, try emailing them so that they will refer you to their websites designer. Before agreeing to a price, make sure that you communicate to the web site designer the number of pages, services the website will offer, etc. Try to make sure that there are no additional fees for logos and charges.
To make sure you get a customized and personalized website from a website designer, make sure that you tell the website designer everything you want, exactly the way you want it.
To avoid ordering revisions, monitor the progress of your website twice a week. In this manner, all revisions would be at a minimal level.
Expect your website to be turned over to you in a matter of months. Completion of the project would obviously be dependent upon the size of the project.
Inform your website designer as well of keywords he/she should place in every page of your website otherwise your website will be hard to find by search engines.
Of course if you are budget conscious, you can always design your own website. But this is only recommended if your website will be small. Even if you are a beginner, there are many web design tutorials on the net that can teach you how to make a website step by step.