I'm using an MVC framework to develop a web site, I've to care about the design in the sense of look and feel (views) and the code (models, controllers).
I don't know what is the best way to proceed:
I suggest you design first - it can be a rough design with a pencil/paper but it will give you an idea of what information should go on the page in what manner. This will help you with your views and controller logic. Dont' worry too much about colours at this point.
I always feel it is better to do things iteratively. Design a page or two, construct the model and controller relative to that page, and repeat for other pages.
Sometimes if you spend too long in your models and controllers and neglect your views, you'll end up doing way more or way less than what you need.
The beauty of MVC frameworks is it simply does not matter.
Obviously you'll need some vision to work to, but it's up to yourself. I'm a strong believer in iterative development. In this case you'd create a section of the site, views, models and so forth. Once that was working, move to the next section/feature of the site.
It depends but there are several rules of thumb:
In your particular case, since I'm not sure about the project size, I'd suggest having your schema designed ahead based on your needs, which will tell you about dependencies, and then do the iterative thing, starting with the dependencies. If you have specific APIs you have in mind, it's a good idea to design around those as well
The both ways are OK but it would be better if you have a designed view (even a mock up) so you can know what data to get how to format it when you develop you model and controllers
My suggestion which will save you a lot of time and headache is start off with design.
You have two designs here. One is the UI (interface) design. All the visuals etc.
When you have a UI design you will know how to create your mark-up from the get go without having to do the work twice after you've completed a design.
The other is the software design. the MVC framework helps a lot with this but you also don't want to just start coding without having a plan. You'll find yourself back tracking a lot and recoding stuff you've already done that way.
The 37 Signals (the source or Ruby on Rails and some really cool web apps) book Getting Real advocates working from the interface down. It gives you a better sense of how the site will be used before you do too much back end implementation.
Here is the specific chapter: From ideas to implementation.
PS: Read the whole book, it's brief and a really good overall philosophy for building things the way they should be build. And no I am not affiliated with them in any way.
One small, but very good tip I got, was to work out what kind of 'friendly' URL's you would like to see in your site. This in turn leads you to what routes your require, which in turn gives you an idea of the controllers and actions you will have to create.
An iterative approach is the way to go. I might suggest spending time on the model and getting it solidified first. Then, iterate through your controllers and views. This will help validate what you've done in the model, and bring up any glaring issues that need to be addressed sooner vs. later.
Understanding the Requirements Database Design User Interface Design Business Logic Design
I, as most here would say design (at least to a extent) first. I would wireframe interactions (these can, and should be be refined later) and, perhaps most important, (at least if it's a traditional web site you're working on) plan the architecture, map the structure of the site you're working on (the Information Architecture part). In order to get an overview of the site and know map out user paths through the content.
That's at least my 'modus operandi' for web sites if I'm working alone on them. (I mostly work in a UX team so my professional workflow is more in the design part than production coding nowadays)