Slic3r Print Settings - Where's the guide?

I'd love to find a guide that gives REASONS why I should choose some of the important settings for my prints! I've been working backward from the troubleshooting guides, but I'm sure that an experienced printer can give a reason for each setting in their gcode. In fact, I'm sure that some of you have reasons for every setting in Slic3r and can say what generally happens to a print (say, in ABS) when you do X, or Y, or Z... Here's where I am:

I've got my Prusa Mendel i3 from Joseph Prusa up and running now, and at first the only good prints I got were the demo prints that come with the software the company sent with the kit.
So I looked around and tried Cura. Not nearly as configurable, but every print has just WORKED.

With the Slic3r setup, the fan is NEVER on - and not surprisingly, the bottom 10 layers or so sort of melt together. and then things start working better. This might also be about the heated bed settings.

I look online and in this forum, and I get examples of settings, but never with obvious reasons why they're set.

Try this: [manual.slic3r.org] and [richrap.blogspot.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Yeah I tried slic3r initially got fairly confused then tried cura a few times but was not completely impressed with the results and went back to slic3r. Once you've got a handle on what each setting does, be prepared to work through several kg's of filament, you'll be much more likely to get great results. Its a very long and at times depressingly steep and treacherous learning curve but very rewarding when it all finally works, until it goes wrong again!

There is a good youtube video of the slic3r settings.

I've looked at a few, but I think the areas I need the most help with are glossed over. I'll start a new topic that gets at my specific issues.
Thanks to you all who gave suggestions - I'd seen the resources you suggested, and I need detailed help on temperature and fan settings.