But to get me started, what would be your top 3 DSLR tips?
The following mostly applies to film SLRs as well, so you will already know, but perhaps will have forgotten, this basic stuff:
1. Support most of the weight with your left hand via the lens, especially with bigger lenses.
2. If you do fancy a semi-auto mode, use Av (Aperture Priority) for most things. You select the aperture, the camera sets the shutter speed. The smaller the F number, the larger the aperture and the shallower the depth of field and the faster shutter speed the camera will select. For optimum lens performance (typically), use F8 when dof and shutter speed is not critical. Dial in some +/- EV Compensation if the first attempt is too light or dark - the camera will then tweak the shutter speed.
3. Keep an eye on the shutter speed to ensure it doesn't get too slow when hand-holding. Rule of thumb for limit to avoid camera shake: 1/50 sec at 50mm focal length, 1/100 sec for 100mm and so on. You can break this rule, but try not to when you can avoid it by using another aperture or ISO setting instead that will enable a faster shutter speed.
As far as using the camera goes, the only major things that are different from film is being able to alter the ISO at any time (in the middle of a roll of film, as it were) and the ability to view your pics straight away.