Some good advice here. so as not to repeat any advice, Ill just add when you go down, you will be shaken. you will question yourself as to your decision to ride a bike. You will have to make that decision then.
gravel hates bikes. so does sand, and water and leaves and grass. Oh yeah and anything loose anywhere you are riding. someone said theres little or no difference between shorts and jeans when a bike goes down. There is. If you are in a low speed lay down, jeans will keep you from getting burned on the exhaust and other hot parts.
buy or borrow a book called "A Twist of the Wrist" It's written by a motorcycle racer, but it has great advice for the street too.
I have owned two bikes, one a 600 yamaha radian the other a 500 suzuki gs. I recommend getting a bike that has enough power to get you out of trouble. 600cc minimum if you ride highways. Any bike can brake hard, having the juice to out accelerate a sleeping, drunk or moronic driver coming up behind you can be worth its weight in skin grafts.