I always have one of these with me [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXWW16&P=0]Load Voltmeter[/link] and use it between flights . After seeing 3 planes lost to battery issues so far this season , it has become part of my preflight routine.
Another item would be a restraint for starting your plane, most Clubs have it in their rules. I used a cargo strap and a long screwdriver or the hitch on my truck.
Special, lucky flying hat and pair of sunglasses and a iced down cooler of beer for your RCU flying buddies and your good to go.