Pack everything you take in ziploc or similar sealable bags. If it rains and you didn't do this... you could be screwed. Even tents leak, sometimes it rains while you are walking, sometimes you just get dumb and leave something outside.
If you are hiking, look up some sites on foods to take. You really don't need a cooler. A friend of mine always took hamburger meat, wrapped it in plastic wrap, then aluminum foil, then about half an inch of newspaper and it stayed cold for 2 days. Results may be different if it's really hot though.
If you plan on taking daily hikes, you can take a larger cooler with some fresh foods and leave it in your car, then stop on the hike and bring things back as needed.
If you have food in large packaging, try getting rid of as much as you can before you go. Things like pop tarts and granola bars can be removed from their packaging and put in one bag. Canned goods could be double bagged, if you're feeling lucky. This reduces any waste you might have to carry back because it can't be tossed in a fire.
Take 3 times more water than you think you will need, and leave a few gallons back in the car just in case. If you drop the water you have, you'll still only have a short hike to get to some more.
Take a few half-empty rolls of toilet paper, and put them in seperate ziploc bags in seperate spots of your bag. If you have them together, and that bag gets wet, have fun with the leaves!
A grill is actually a good idea if you don't mind carrying it.
Don't forget fire starters and matches/lighters. Don't waste time searching for kindling and doing it the old fashioned ways if you don't have to
Even though I haven't been in Scouting for 6 years, I still take my BSA handbook and pack by its checklist. If anything, it's some good reading material to pass the time if you get bored.
