My favorite piece of advice is to carry lots of small line and rope. I have personal experience with this. Somehow the pin that hold my tiller extension on feel out while 10 miles from where we had put in and the wind was giving it hell. We were able to rig up a new connection with some small line.

Also lots of pins shackles and bolts. If you see something that you can think of a way to use it, have it in the car. It will make sailing much more fun when you can just fix it and head on your way rather than cancle the whole day.