Nothing beats learning about skinning than opening up the files and checking them out yourself and understanding the code. The skinning documentation, although people say it's not been updated etc. it's really been very well written and that is how I got started about 4 years ago and the principles in many situations still apply.
You can use Dreamweaver to create skins if you are graphically/designer inclined. I have several resellers, marketers and clients who have a Mac - there are work arounds. You can work in html or if you want to do more advanced skinning, sometimes learning the ascx method is helpful as when you learn more, you can drop in code to extend the skin just that little bit further and by linking the CSS file when working, you can see the output on the page in most instances.
I'm not buying into the argument about tables or no tables either in spite of my comments on this post, I won't be commenting any further. I have my own opinion on this whole concept which seems to be shared between designers, not the clients. I've NEVER been asked by the end user client about providing xhtml skins, but it's a fantastic bandwagon to jump on. I genuinely appreciate open source xhtml skins - I really do, and I study and analyse them for commercial alternatives for clients, but tell that to the marketing and branding division of a corporation who insist on pixel perfect replication of their information and it's a whole different ball game. If xhtml purity is what you're after with funky designs, then joomla might be the way to go, but hey - who wants to look like joomla all the time?
People use DNN for it's amazing capabilities, and if it's not xhtml perfect, we can work on that area, but in business, clients will often be more insistent that their skin looks like they want it to. And if tell them they can only use a couple of modules in their whole DNN site or they lose compliancy - then they get a better understanding.. an xhtml compliant skin isn't worth the bytes it takes up on your computer if you're not prepared to forgo most of the modules that are currently in existance. Yes, things are changing.. fantastic, and it's great, we need to and we move forward ever improving our process, but let's get Mike off to a good start for him to understand about skinning and the concepts of it with some examples to at least look at and get a grasp on it.
I've got some skins you get started with Mike, I admit, without shame, they are not perfect, not necessarily compliant, not all working perfectly across browser, versions of dnn or even macs - (you did hear about the whole generation of DNN sites that have no menu when using solpart which, until not that long ago didn't even show) ... but you know what - it's going to give you some thing to look at - There are over 50 skins, each with previews - it took me a few months to get going and I have some exciting new skins in the near future, which I am looking forward to sharing. Not all the skins are my own design OK - I'm not taking credit for them, but it's a great opportunity to have a look at some of the layouts, but I do have some very popular skins that I have seen variations of on many sites.
http://www.dnnskins.com/previews.aspx - This is a site I have created to help newcomers to DNN at least get to preview, each image links to an online preview. You can then register and download and see if you can't get inspired or grasp a little more to help you understand it.
I'm really happy to see more Mac users coming in to the fold and enjoying the dnn framework which, until recently wasn't the case. If you have FTP you can upload a skin to a test url and test it, we don't always use our local builds to test skins, You can set DW to view the CSS file while working on it, you won't be able to see the menu structure, that's css, and, by the way - if you're working like that - then caching is something you need to be aware of - my Mac colleague told me that to avoid caching the CSS he actually linked it to another static site - so it was calling CSS from another location, and found that updating the CSS and using Safari or Firefox for previewing was a help. I found that with my Safari browser it tended to hold on to the skin style and CSS more than with IE.
If you work in ASCX mode, you can ftp the skin file and refresh, and if you use html you'll need to be logged in to 'reparse' your skins.
You'll also need to have good xml knowledge to make a difference, as this is required to do alot of the extended skin formatting to bring the css changes into reality - eg.. the ASCX skin is created by the dnn skinning engine, when you upload a html skin, but to make the css classes apply in many areas, you'll need to bind it to an xml file so that the output is written into the ascx file.
But I digress - I could talk about the real world scenarios for days... because when you're running a business, that's what you have to deal with, but I admire and respect those who have the month of sundays spare to try a rubiks cube of code methods and styles to then put that file back in the folder for another attempt 12 months down the track.. We will get there, but don't get sucked into perfect, just start the journey with something that will give you some successes. There is also a large group of people who come into DNN and ditch it because it's not xhtml compliant to their expectations, because they 'feel it should be'... I've got plenty of email from those sort, and my answer, might sound harsh and it's - SO WHAT - the guys are working on it, doing what they can.. use joomla or something else if that is your main goal... and get over it.. DNN is simply outstanding for what it does.
Oops.. does it sound like I've been talking to someone like that recently - Someone said I'm biased... and I said.. Hell Yeah.... I am.
http://blogs.ninameiers.com/2007/07/16/Failed+Validation+But+The+Public+Keeps+Buying.aspx here's my take on the whole thing - but what do I know - I am but the end user. 
Nina Meiers
Lots of Free skins... Really..