Urgh, I wouldn't want to be learning div layouts all over again... there are so many preachy, waffly guides out there.

All I can suggest is sitting down with notepad and starting from scratch... don't allow yourself to use any tables and see how good a page you can make... keep building on what you know until you can feasably ditch table layouts.
You might find yourself thinking "If I was doing this with tables, I'd be done by now", I know I did... a lot.
But I think you have to forget everything you know and lower your expectations while you learn this new mindset, otherwise it's just frustrating.
It's hard to change from thinking in tables to thinking in divs, but it's well worth it.

I think the key to being able to see what you're doing and understanding divs is adding a border:
border: 1px solid #000;
to your div's CSS... then playing with size, position, nesting, backgrounds, padding, margin, float, clear, etc.

And if you get in trouble, just slap different coloured borders on everything (even <p> if you have to) and you'll soon see what's wrong and where.

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