can someone shed some light on thw optimum settings to shoot
moving objects? like a high ISO or shutter speed or? many times the
images appears grainy or noisy (like sv550).I'm using a canon
btw.

High Shutter Speed - optium setting to shoot moving objects like
buses. But of course at the same time, there should be some amount
of strong sunlight. Experiment, but try not to go
over 1/1000 or 1/1600, depending on how strong the
sunlight is.
High ISO - more grain/noise in your photos. Highly not recommended
during the day, but you can still try to set a small measure of the
ISO (ISO 200 and below).
Right, in the case of settings, I normally like to use Av set at
f/5.6. Reason being the rear of the bus will not be blur in my
photo.