I know this is probably a silly question, but what are the basic vehicle controls on sl?

[Lezxy1994]

I have used the arrow keys , but I seem to have a hard time controlling the vehicles

[Rolig Loon]

It all depends on the vehicle and how it is scripted.  Most vehicles do respond to the arow keys plus PgUp and PgDn.  If you have WASD enabled in Preferences, you'll find that those keys substitute for the arrow keys.   Some vehicles will work in mouselook, but those are harder to script.  If you find one, you can often move forward or backward with arrow keys and control your turns with the mouse, once you are in mouselook.

No matter which control system you use, it takes practice.  Some vehicles have very delicate controls, too, so it takes a LOT of practice to keep from overcompensating and driving into obstacles (or off the edge of the world).