Like Al I usually tip the coutesy shuttle driver a $1, more if he handles my luggage.
Porter- $1 a bag, more if he has to use a forkllift.
Restaurants (not fast food) generally people tip between 15-20%. My method- the sales tax in LA is 8.25%, so I double the tax and round it up - approximate 17% - a quick and easy way to figure out the tip and no fingers required.
I like Al's suggestion of Santa Monica Beach, a great day trip. It's about 8 miles from the airport so you may need a cab, if only for the ride home.