If you have "correct spelling automatically" checked and it doesn't seem to be working, it might be because you're trying it in an unsupported application. E.g., I can use the feature in TextEdit and Pages but not, e.g., FireFox or SublimeText 2 (two of my most used apps).
Tho I've spent way too much time looking, I haven't found any way of getting the suggested spellings from the context menu with the keys alone. The best option I've found so far is to use my thumb on the track pad to position the mouse and then hold
ctl and tap (again with the thumb). It takes a bit longer because of the need for positioning, but at least I can keep my fingers on the home row.
I find it awkward to reach the
ctl button, so I've used KeyRemap4MacBook (which is generally awesome and free) to customize the layout to make
caps lock be
ctl. KeyRemap will also let you assign
ctl + click to button combinations, so you don't have to tap/click.