(1) A warm jacket to keep you warm so its possible to function and in one of your pockets carry a set of hand warmers so you can warm your hands up when there is a break!
(2) You will need to find some nice shady spots. When the sun is right in a person's face, it causes lines and shadows that will not create the best photo. To avoid this, place your subject with their backs toward the sun causing a halo effect.
(3) Have an assistant that will make you laugh and place things on top of your head while you're working to make your subjects laugh!
(4) Bring a blanket for your two lovebirds to snuggle up in!
(5) Bring a stool (especially if you're shorter than your clients! It helps to get different perspectives in photos. Most of the time it is more flattering on your subjects when a picture is taken from a little bit higher.
(6) Bring your leg muscles! Make sure you feel that burn when your shooting! (I call it my exercise...but its really just an excuse not to go to the gym)