Headlights
As with most of Europe, it is not customary to drive with headlights on during daylight hours. Other drivers may flash their headlights at you and pedestrians may gesture with their hands to let you know they are on.
Slow Lanes / Uphills
When there is more than one lane on an uphill section of highway, the outside (right-hand) lane is usually a slow lane which is identified by a broad dotted lane-separator line. Other drivers will expect you to pull over into the slow lane unless you are overtaking a slower vehicle already in this lane. These lanes are usually limited to a kilometer, and merge back into the fast lane. Most North American drivers would expect that drivers in the fast lane would yield to slower drivers, but it is opposite, you must yield to cars in the fast lane. Sometimes a minimum speed is painted onto the road surface at the beginning of each lane.
Overtaking
Overtaking is a common dance in Spain. Fast drivers will often pull to within a few feet of the back of your car, overtake you, and pull in with only a few feet to spare. Our advice is to go with the flow and let them! If you can see the road ahead is clear, and someone wants to pass, putting your right indicator on will signal that it is clear to pass.

If you are overtaking (a large truck most likely), then use your left indicator as you are passing. If a truck is overtaking you, then you can flash your lights once when the trailer is clear of your car. This will indicate that the truck can safely pull in.

Speed Limits / Fines
Speed limits are posted on signs at the side of the road. Generally, the speed limit is 50 Km/h in towns, 90 Km/h on open roads, and 120 Km/h on highways. These limits are absolute--you will be pulled over if you are 3-5 Km/h over! Although many local citizens speed, following them will not help reduce your fine. Police often patrol cars at the entrance of towns where the limit drops to 50, make sure you reduce your speed before you enter any towns. There are 2 types of speed signs you will see: the first posted inside a red circle. These are absolute maximums, do not go faster. The second are inside solid blue squares. These are suggested speeds posted at corners, bridges etc. and are not strictly enforced.

If you are pulled over, you will be required to pay ON THE SPOT. It is a very good idea to carry some cash to cover such a case. You will also be required to present your drivers license (an international license is not currently required for most countries).
Gasoline / Petrol
Firstly, make sure you fill your car with the right type of fuel - diesel or regular! If your car uses regular gasoline, make sure you are using unleaded, as leaded gasoline still exists at some stations.