[Halcyon]

To make a proffesional website you should first look at other bands websites to get some ideas and then come up with your own idea that is different and offers a unique touch.
You need to think why people would come to your site in particular and then start to design it.
Do rough drawings on paper of the layouts and sub pages that you want coming off it.
Think about how you will organise it and how it will be broken up into different sections.
People will not stay on your site if it takes them more than a couple of clicks to find the information you are looking for.
They will also be put off if they are hit with anything that puts the reader off.
So, to keep it proffesional make sure you make it compatible by testing it in more than one browser, keep fonts the same and use appropriate colours / backgrounds that are easy to read and not impossible to see.
Organise the site well so that it is easy to navigate.
Don't put in any java scrolling banners or host your site with a company that launches a billion adverts at you.

As for what programs to use......There ar eplenty of freebies out there but paid for software is the one I'd recommend.
Macromedia Dreamwaever, now owned by Adobe I believe will let you design the pages, layout, and style of your site in a what you see is what you get style, as well as letting you input your own html and scripting too.
You can then add images that you've prepared and saved to the right size in any photo editing package, eg. Photoshop.

Flash content can be created in a variety of programs. If you want a free option, I believe there is a program called Swish that let's you make flash creations.
The main software I'd use is Macromedia (Adobe) Flash.

You need some time to master it but in a nut shell you basically draw things on different layers and choose how long these images appear on a timeline. You have several scenes that make up your flash movie and you can then animate content by creating different omvements at different key frames, etc.
You can also add Action script which allows you to create numerous flash content buttons, forms, effects, applications, behaviours, etc.

your best bet is getting a good book that will come with a library of actionscript and creating your first movie tutorials.

Once the flash content is done, you render it into a .swf file and just like you would an image, you insert it into your webpage layout.

Have a mess around with it.
There are plenty of flash tutorials that will get you going with the basics.
Once you know how to use the software a lot of it comes down to your own website design and how you will use the software to implement the design.