Find your local highway act and read it.
You'll likely see that it has a section that talks about bicycles, and very likely says something like "Bicycles are to ride as far to the right as practicable." As far to the right as practicable usually means something like ... ride on the shoulder, if there is one, or as far to the right in the lane as possible without running into road debris, grates, etc. if there is not one.
In other words, you are to follow the rules of the road, except where the highway act says differently.
As for stopping behind a vehicle at the lights ... you don't stop directly behind ... stop behind and to the right ... by the right rear corner of the vehicle. That way, if a car does want to come right up behind the car in front of you, it can, but it will have to give you room.
And ... use reflectors ... wear reflective gear ... wear bright jerseys and bright helmet. Remember what I said earlier ... "Always ride assuming that the drivers of the vehicles don't see you." But do what you can to make them see you.