Many blogs and other sources of information on cycling advocate "riding like a car" or "taking the lane" as a way to increase safety and visibility when riding on a road. But such advice presupposes that doing so is legal.
Is it generally the case that bikes may use the "full lane", or is it better to check with local ordinances? Is there a general rule of thumb one should apply in cases where one is not certain about local rules?
For any question about law, you always have to check local laws.
The general rule is that you go with traffic and ride as far to the side as safe, taking the lane when it makes you safer. In many places this is how the law is written, but even when it isn't you may wish to do so.
From what I recall of the League of American Bicyclists safe cycling class I took, in the United States you're allowed to "take the lane" basically anytime that doing so is safer. The exact laws vary from state to state, but they all basically allow this same behavior.
Reasons to move away from the side include:
Whether or not you're required to use a shoulder or not is different in different states. In California you're allowed to use a shoulder, but not required to; a narrow lane and wide shoulder allows you to legally use the full lane (but riding on the shoulder might be better).
Police often don't know the proper rules for bikes and mistakenly think you're always required to ride as far to the right as possible. Other road users often have that same problem.
The key phrase to look for to learn more is "vehicular cycling". There was a big move to vehicular cycling in the 60s and 70s, an I've noticed many laws that make it explicitly legal date to the 70s.
To give you a UK take on this, without the legalities involved, we have to share the roads whether we like it or not.
So, try to give passing traffic room to get past, but leave yourself room to maneuverer and be safe. But road conditions and traffic flow is a constant ebb and flow. Do what feels decent for you first and other traffic secondly.
Sure, sometimes we all get squeezed down by passing traffic but you can't expect the car behind you to sit there for miles if you hog the lane. It's a fine line and it takes sense and practice.
Stay safe out there.
So far as I know, in the most if not all states in the US it's legal. The laws may specify "as far to the right as safely possible" or something like that, but they generally leave it up to you to evaluate what's safe.
Minnesota law, eg, states:
Subd. 4.Riding on roadway or shoulder.
(a) Every person operating a bicycle upon a roadway shall ride as close as practicable to the right-hand curb or edge of the roadway except under any of the following situations:
(1) when overtaking and passing another vehicle proceeding in the same direction;
(2) when preparing for a left turn at an intersection or into a private road or driveway;
(3) when reasonably necessary to avoid conditions, including fixed or moving objects, vehicles, pedestrians, animals, surface hazards, or narrow width lanes, that make it unsafe to continue along the right-hand curb or edge.
The problem, of course, is that you may encounter others (both drivers and law enforcement people) who do not interpret the law this way (mostly because they've never read it), but that's a problem for all cycling-related laws.
In Ontario:
HTA 147 - Slow moving traffic travel on right side
any vehicle moving slower than the normal traffic speed should drive in the right-hand lane, or as close as practicable to the right edge of the road except when preparing to turn left or when passing another vehicle.
For cyclists, you must ride far enough out from the curb to maintain a straight line, clear of sewer grates, debris, potholes, and parked car doors. You may occupy any part of a lane when your safety warrants it. Never compromise your safety for the convenience of a motorist behind you.
"is it better to check with local ordinances?"
I've read that statutes about driving on the sidewalk and sharing with pedestrians varies (in North America) from city to city; but I expect that statutes about driving on the road vary less, and are set by the (larger) State (or Province, or Country).
Some roads are 'no cyclists or pedestrians' and signed to that effect.
I'd guess if you're going somewhere unfamiliar you should find out the local laws and customs.
This depends on the local situation I'd say. for instance the German road traffic act (StVO, Straßenverkehrsordnung) says in §2:
(2) Es ist möglichst weit rechts zu fahren, nicht nur bei Gegenverkehr, beim
Überholtwerden, an Kuppen, in Kurven oder bei Unübersichtlichkeit.
(2) One has to drive as much on the right side as possible, not only with
oncoming traffic, at hilltops, in corners or on complexity
Source: http://www.gesetze-im-internet.de/stvo/__2.html
That rule is not specific for bikes but all sorts of vehicles which are allowed on roads.
Besides the legal situation: Going on the right makes it simpler for faster cars to overtake one. When driving too much on the left car drivers can, in my experience, become annoyed easily. While one should be riding at the edge of the road but keep some space to the right so one can navigate if there are issues on the road.
In Downtown Spokane (Washington State) we actually have a one-way road with a bike lane and a posted sign that says "BIKES MAY USE FULL LANE".
On approach to the sign this road is three lanes wide and then gains another lane right before a stop signal. The sign is placed exactly at the place where the fourth lane is added to the road. The bike lane disappears into the fourth lane at the sign.
On almost all the roads in Downtown Spokane, bikes are able to use the roads, especially on the less-busy three-lane one-ways. I frequently ride my bike in the Downtown area, and drivers are generally very willing to allow me on the road with my bike (except when riding a bike on Division Street or 2nd/3rd Avenues). Usually the less-driven downtown roads are good for using any lane.
Spokane is a pretty nice city if you have a bike. I would say it is okay to use the full lane on a road in your city, but only if conditions allow you to move as fast as the cars. In Downtown Spokane the area-wide speed limit is 25 miles per hour, and usually traffic moves much slower than that. But just to be safe(r), I take the three-lane one-way roads that nobody else likes.
