I've read that this can be done with greater ease by using Ready Image, but since I'm more familiar with PS, I shall use PS as the guide.

This guide does make a few assumptions ::

1) You already knew how to use Photoshop.
2) You already knew how to write HTML codes
3) You knew both of the above but did not ralise that it can be done ..

Thus, I shall not touch on those 2 topics, as books a thousand pages thick have been written on them. So, I would wanna waste my time and yours and all the disksapce that could be used to host some useful stuff.

01:. Open the .PSD file which you have created the layout on.
Somethings to take note of::
You may wanna toggle the "Snap" function in the "View" in the menu bar
"Snap" will snap on to the nearest border. So if you are making very fine slices, you may wanna disable it.

02:. Create the slices
I'll usual hide all the other tools when working and this can be done hitting the "TAB" button on your keyboard.
I'll also like to start from outside the picture as it will snap automatically back to the border of the pic
* Do note that HTML creates tables in row-by-row manner .. so try to keep your slices in rows .. this will make your editing of the code a lot easier in the future

03:. Edit the slices by doin a right-click
* If there is no special formating or pict in the slice .. ie .. pure text or palin backgroud, it would be best to change it to non-image
* HTML can be included in the text box

04:. Save as HTML
Press "Ctrl" + "Alt" + "Shift" + "S" or goto File >> Save for Web
You will then be able to edit the pict quality of each slice..

05:. Do your own refinement of the Webpage with your preferred HTML-Editor