It's not a secret that most users judge websites by their appearance (first) and their content (second). It's true that your content it's the most important thing in getting new visitors, but the aspect of the website is the second main reason those visitors will return to read more. Allong with great content, getting your site (or sites if you have more than one) visually appealing will assure the flow the visitors, and in order to be appealing it has (they have) to be user friendly (the most important thing), navigable, attractive and organized.
There are some web designers or website owners that do not care about how their websites looks (not enough or not at all), they are interested mainly in designing and developing websited that function properly.
There are a few tips about how to make you website(s) to be visually appealing:
Plan ahead how your website will look and function
The first thing you should do when designing a website is to plan ahead how your website will look and function. It's easy to install a Joomla or a Wordpress (for example) and have an online wel configured website in less than an hour, but usually it's not enough: you have to get the best theme for you installed CMS (from the existing ones - there are "only" a few thousands or to design one from scratch).
As an experienced webdesinger I can tell you for sure that the different between a client that knows exactly what he wants and one that is trying to find out while the website is being developed is huge. I've got both of them and the previous sentence is the "voice" of experience.
Establish the target for your website
In matter of interacting you other people you must already know that you can say the same thing in several different way - they have about the same meaning, but it's not the same thing. Jokes are in many cases very common things told in a funny manner that is hilarous, they can even get people shocked in some degree.
The same thing apply to websites: there are several way to send the same message, every way is translated to a different template to your website. Each template can be visually appealing for one category of people but others will not like it at all.
Keep your design simple
People love websites with vivid colors and images (using heavily CSS to do this is recommended), but in the same time they don't iike websites that are too crowded with visual elements and texts all over the page. They need too navigate freely on site and to understand it quickly in order to love it. No websites full with images (especially the kind of images that's going from one corner to another), too much text and, especially, with tones of advertisemens is visually appealing to the users.
Use graphics, colors and images
As I said, people love websites that contain graphics of some kind. CSS is the best thing for this, and the new tools for 2012 will definetly help you get a better visual appealing website from this point of view. Probably the most important new tools among all is HTML5, so keep yourselves informed about it.
Keep the visual consistency - be consistent in your design
You should consider not only the website consistency, one most important things from the perspective of the structure of the website, but also the visual consistency. Apply the same rules to your design in order to get it visually appealing: all your fonts, text formats, link colors label, graphics and page format should be the same all across the website.
The most important thing you should remember about webdesign is that you should put in your visitors' shoes. You are designing the website from your own perspective, so you must be proud about what your product and you have to love it in order to get the best product, but you are also designing it for your users. Always try to get their perspective in order to improve yours and to improve your websites.