To make the structure of your page you generally want floating (and then margins to exactly place it).
Absolute positioning/relative should only be used for dropdowns/small design segments of the page (aka rounded corners or some other small effect)
Absolute positioning should never be used as a page layout technique for columns because if you have a footer it will be a mess and the contnet will probably end up overflowing on top of hte footer. It's not suitable for dynamic environments :).
If you go to pmob.co.uk where a regular here (Paul O'B) has posted many layouts, you will see every single one of them is done via floating and margins. It's by far the best layout technique and even though it has more bugs accompanied with it (as apposed to absolute positioning) it's still better (99% of all bugs have been documented and fixes are relatively easy to impliment, making this method the easiest)
HTML table layouts should nevner be used because table layouts are only to be used to display tabular data and as a result it would be unsemantic to use it as a design for a layout (even though sometimes tables would be the easiest, aka equal height columns, and other behaviors that are table specific)
Don't get me wrong, tables are completely fine if you have tabular data on the page (aka a data table of...oh..for example, all the speedcubers (rubiks cubes) that are competing in a competitiion)
It's your call whether it's tabular data. The key to making good pages is to not have divitis (overuse of divs) or any other "itis" :). As long as you don't bloat your markup and write clean code (CSS hacks generally aren't needed because most bugs don't require hacks :)) then you are sure to write an A-grade page :tup:)
As with any profession, you will get extremely good at it in time. Assuming you are a beginner (take no offense if you're not :)), as you code a page you should try and refresh the page in a browser every segment (every peice) of hte page until you see exactly what everything is doing. You will learn to code bug fixes into your page as you are coding. But then again, that comes with experience. Give it time :). Eventually you can code an entire pgae cross browser (99% of the time)
If you have any questions related to a certain thing happening on your page then just feel free to ask here :). It'd be a good idea to start getting in the habit of visiting this forum frequently (CSS forum in particular) because we go over many issues and eventually you will start to notice the same problems comiong up. You will learn the fixes (in time) and you will get dramatically better because of it :).
If you need any CSS reference help (a property/value etc) then visit the Sitepoint CSS reference :)
Hope that helps