You can also strafe — walk sideways without changing your camera focus — by holding Shift ? and the left and right movement keys. For example, Shift ?+←. Instead of turning, your avatar will walk in those directions.
Running is done with the same keys as walking. Running is usually a toggle: press Ctrl+R and try moving around!
Jumping and ducking
Tap Page Up or E to jump.
Hold Page Down or C to duck (squat).
Tip: After jumping, hold down Space to slow your ascent dramatically. It looks almost as if you're frozen in mid-air.
Holding the same key to jump makes you fly.
Tip: If that doesn't work, go to Me > Preferences > Move & View and enable Arrow keys always move me.
You can also select Move > Fly from the toolbar at the bottom of the Viewer window.
Note: In Second Life, there's no effective height limit to flying. Unaided, an avatar can reach approximately 200 vertical meters, but if you've got a flight assist script, you can continue to propel yourself upwards to millions, even billions of meters. See also Limits.
If you don't want to always run, you can make your avatar walk or run with use of your arrow keys. Double-tap and hold the up arrow key to run forward. Tap and hold the up arrow key again to walk. This feature gives a more realistic appearance to avatar movement.
To enable double-tap run:
Open Me > Preferences to open the PREFERENCES window.
Vehicle operation varies widely; consult each vehicle's specific manual, or ask the creator for help. You can however operate most vehicles by right-clicking and selecting the appropriate option. Your avatar is seated in control of the vehicle, and the same directional keys used to control your avatar are now operating the vehicl, as shown in this video:
All capable vehicles are scripted; there is an amazing array of possibilities. Vehicles come in physical and non-physical varieties (although some can "switch" from one to another as-needed for specific purposes, like dampening the adverse effects of region crossings).
Physical v. non-physical vehicles
Physical vehicles behave according to Second Life's physical rules. For example, if you drive a car over a ledge, it may coast for awhile due to the momentum propelling it forward, but gravity acts upon it until it hits the ground. Physical vehicles must be 32 prims or fewer (see Limits). This prim economy makes vehicle-creators quite savvy and resourceful about how each prim is used in vehicle's overall construction.
Non-physical vehicles can be 256 prims or fewer (see Limits?), including the driver and passengers, each of which counts as a prim. Since non-physical vehicles are not affected by physics, their motion may appear stilted and stiff, although their visual appearance may be more detailed. This generally makes "non-phys" vehicles a better choice for floating UFOs and large warships which don't need to interact with collisions and other kinetic behaviors.
The best way to understand is to learn, so try out various vehicles of each type.
Where to use vehicles
Your vehicle can go just about anywhere your avatar can go. To rez a vehicle, you need to find a buildable parcel of land (make sure that there is no icon in the menu bar that shows a prim with a slashed red circle on top of it).
There are many public roads and waterways constructed by Linden Lab to enjoy traveling on. Some of these are marked as Protected Land (shown as the parcel name in the menu bar); others have been crafted by the Linden Department of Public Works.
Scripting a vehicle
If you are interested in learning how to script a vehicle yourself, the Linden Vehicle Tutorial is a good place to start.
Troubleshooting avatar movement
If your avatar begins moving erratically or uncontrollably:
Try logging out of Second Life and restarting the program.
If that doesn't work, try right-clicking on yourself and selecting Take Off > Detach All to remove your attachments. Then, try relogging. Scripted attachments have the ability to affect your avatar's movement, so always try to make sure you know what you are attaching to yourself!
If you have dropped an object on the ground which is animating your avatar, follow these steps to stop the animation:
Locate the rezzed object.
Right-click on it and select Take.
Locate the object in your inventory, right-click on it and select Wear.
Detach the object.
A simple wear-and-detach can often "reset" unexpected scripting problems in attachments.
If that still doesn't work, try unplugging your modems and routers for a full minute, then plug them back in and log back into Second Life.
If you get stuck in something (like a box or a cage):
Look for the ground or an object in the open. Right-click on it and select Sit Here. It takes a few seconds, and you may hear some bumping noises, but your avatar should magically fly out of there soon enough. If that doesn't work, remember that you can always teleport somewhere else to escape!