I am currently working on a project where a lot of user interaction is going to take place. There is also a commercial side as people can buy certain items and services.

In my opinion a good blend of user interface, speed and security is essential for these types of websites. It is fairly easy to use ajax and JavaScript nowadays to do almost everything, as there are a lot of libraries available such as jQuery and others. But this can have some performance and incompatibility issues. This can lead to users just going to the next website.

The overall look of the website is important too. Where to place certain buttons, where to place certain types of articles such as faq and support. Where and how to display error messages so that the user sees them but are not bothering him. And an overall color scheme is important too.

The basic question is: How to create an interface that triggers a user to buy/use your services

I know psychology also plays a huge role in how users interact with your website. The color scheme for example is important. When the colors are irritating on a website you just want to click away. I have not found any articles that explain those concept.

Does anyone have any tips and/or recourses where i can get some articles that guide you in making the correct choices for your website.