No doubt you all use a mixture of many tools, but no doubt some are your favourites.
By tools I mean things like aperture, camera height and angle, background selection, focal length, exposure...
1. Camera height, angle, orientation and distance to the subject is my starting point, which will be driven by how the main subject elements visually interact, as well as the lighting patterns and the relationship between foreground and background elements.
2. I mainly only use 2 to 4 prime lenses, so at this stage I will select which lens to use. Choice of lens will depend on how I feel during the step above.
3. I tend to then revisit step 1, when I might change lens, but not often.
4. I then think about aperture and how different depths of "depth of field" will affect the image. I often use the stop down button, not to really judge depth of field but to check for elements in the background or foreground that might distract in the final image.
5. shutter speed is next and I think about how much subject movement I need to stop or maybe accentuate.
6. Exposure comes next and I try to work out the relative importance of highlight and shadow detail to the final image.
7. I then usually have a juggling act between aperture, shutter speed and ISO, to get the balance I think is right for the image I want to produce.
8, Before pressing the release I try to visualise the image as a finished print, which more often than I like to admit, will often send me back to step 1 ;-)
Edit: Mmm, I missed out what is probably step 2a. I normally compose square, but some where between steps 1 and 3, I may well revise this and switch to 3x4 or 2x1 (I dislike the 3x2 ratio, and only occasionally use it) I also very occasionally do a panorama.