how you make sure, define what customer wants?do you use a web design form and write every single detail?
what if they turn and say we did not mean this way,that way…
You need to communicate with your client extensively before committing to a project and working with them.
Ask them some questions find out what sort of client they will be, responsive, hard to work with, lazy etc.
Ask yourself if you can work with them you don’t want a project that is going to cause you grief it can suck all the fun out of work and this will affect what you produce to them.
Once you have decided to go ahead with it (or not) you should go through several stages of the design process.
I do something like this:
Sitemap (figure out all the pages in the site and an intended user journey through the site).
Wireframe (I produce two wireframes, one for the homepage and then a standard page template.)
Page Design (presented in browser)
At each of these stages I get the client to review and make minor changes as I have already spoken to the client many times and have a good idea of what they want.
With the wireframe and page design once they sigh off on the initial two designs I do the rest.
That is a very basic a simplified way to go about it. Smashing magazine have a good article on this which you could google for and I am sure loads of other helpful articles will appear.