How to deal with parked cars - overtaking a parked truck or bus:
Approach as described above but with extra care. initially try to look under the vehicle to see if there is anyone working behind it, then check along the left side for pedestrians that may walk out. Then, as soon as possible, move out to the right so that you can see past.
"Early position, early view".
If you see something approaching you can always pull back in again. But if you pull out late, you may pull out into something you can't see. As you approach be certain that it hasn't got a tailgate partially down. A tailgate may stick out towards you 2 metres and be almost impossible to see if it is at your eye level.
As you get alongside, slow down and be prepared for anyone walking out around the front of the vehicle. Cover your horn.
Buses deserve special consideration as they usually only stop briefly. If you see one pull up, try to see how many people are waiting to get on. A number of people getting on will take some time to pay their fares, unless they've got bus passes! People getting off will normally do so quite quickly. When you go past a bus, go slowly, and be especially careful of people walking around the front of it. The longer it's been at the bus stop the more likely this is.
Because buses have automatic gearboxes (some are semi-automatic) the driver will sit with his foot on the brake to stop it creeping forward. When his brake lights go off he is probably about to pull away. He is likely to then indicate as he begins to move. If you see a bus about to pull away, let it go if you can. But, you don't have to. Just be aware it may go anyway, even with you alongside it.