I know a lot about HTML, and one of my friends wants me to show her how to make a website. I have been designing websites and creating message boards for about 5 years now, but I've mostly worked with pre-determined templates. She's an artist and wants to make a website for her artwork. I can get her a domain and help her code it, but I don't know what the best way to do this would be. Does anyone have any recommendations on how I should go about doing this? I want to impress her, so what would be an awesome design idea(s) I could use? Thanks in advance.

"How can I make a website like a professional?"

The best way is to look around the web, see what you like, and try to emulate. look at a site and try to figure out what the builder did to create what ever effect you are looking at.
RMB --> view source
gets you usually the complete source of a page in HTML, which you can use as a base template again.

Or hire a professional

Note: She wants to be able to sell her paintings on the website.

Use Timecube.com as a general outline.

professional looking vs creative looking

If it's professional looking that you want, studying and copying the style of other professional looking website is the way to go. There is no more shame in that, outside of creative websites that want to burst through boundary of design, every other websites look the same in term of style, no matter what colour or images you put.

I'd maybe actually suggest learning flash. A lot of nifty flash-intensive sites out there, and that would allow for a lot of things that are a lot less do-able otherwise.

Flash has a lot of major disadvantages though. Some of the main ones being that it isn't indexable by Google and I am fairly sure a lot of people just give up looking at a site when they see it is made in flash. I know I do.

TBH though, there isn't much flash can do that html and javascript can't. The main plus is it is probably easier to make something that works in IE6.

Here are a couple of templates you might consider with the latest style and pizazz:

http://www.lingscars.com/

http://www.americanbeautybordercollies.com/

http://www.cafeintl.net/

http://www.mrbottles.com/

http://www.georgehutchins.com/

http://anselme.homestead.com/AFPHAITI.html

http://www.thomasedison.org/

http://www.havenworks.com/

http://www.maisonmartinmargiela.com/

http://yvettesbridalformal.com/index.htm

These are related to art
http://art.yale.edu/

http://www.joneschijoff.com/

Here is the best one I think
http://www.dokimos.org/ajff/

Seconded.

Something like this: http://www.havenworks.com

Avoid Flash / Java like the plague.

When possible, use CSS instead of javascript.

Don't go into extremes, extreme minimalism can be just as off putting as whatever is happening on that havenworks site.

Don't integrate Facebook, Twitter, Digg. If you have to do that, make it non-intrusive for the user. No one likes having a hundred "WOULD YOU LIKE TO POST THIS ON YOUR FACEBOOK WALL????" pop in your face while browsing a site.

Use the latest web standards. Use CSS3 and HTML5 if you want but don't forget that not all browsers support it, use an extra stylesheet for outdated browsers (Internet Explorer pre version 9)

That's all I have for now.

well one more tip... while designing the site, create vector graphics instead of bitmaps. You can then later convert them to whatever format you want. Pixels = evil