Equipment Tips
Trek America recommends various things in their TrekTips section, so please read that first! This is just a list of things which I found really useful on the trip, or would have liked to have
Therm-a-Rest self inflating matress - This made sleeping so much more comfortable! TrekAm do provide foam mats, but they aren't a patch on one of these guys. They are pretty expensive, so if you never intend to camp again, it might not be worth it.
3-Season sleeping bag - TrekAm say you must bring a sleeping bag, and I would strongly recommend no less than a 3-season bag as it can get pretty cold at night in the mountains.
Small LED Torch - Very useful for getting around at night!
Chargers - Dave had an inverter in the van, so we could plug in camera / ipod chargers etc. With the amount of photos being taken, this was very useful! Don't forget a UK to US plug though.
Cheap multi-tool - I found it quite useful having a multitool with me for various thingss. Don't go buying a Leatherman, but a £9.99 one would be handy.
Platypus - I personally love these water systems - handy for hiking and biking.
Life Venture Waterless soap - This is a gel with which you can wash your hands without having water. Very handy when up a mountain and wanted to eat or whatever!
Mosquito Spray - I used Life Venture Expedition 50+ (repellent + insecticide - 50% DEET) and I didnt get bitten once. Some people were eaten to death!
Waterproof document wallet - If you dont like leaving your passport / money in your rucksack, I would get one of these (Note that rucksacks are left on the bus quite a lot). I wore mine pretty much all the time.
Waterproof Jacket and Trousers - Hopefully not needed, but awful if you do need them and dont have them!
Food & Drink Tips
The food kitty provides breakfast / lunch / snacks (fruit and grenola bars) / dinner. However, no soft drinks / alcohol or puddings are provided.
If you intend to drink alcohol (there is no obligation to - I didnt drink at all on the trip), buy crates of beer before crossing into Canada - it is much cheaper in the US.
I personally would plan to buy chocolate, Sprite, brownies and whatever when your over there, as its nice to have and people tend to buy stuff to share around.
Be prepared to try some new stuff! If you have fussy eating habits, get over it, as you will probably starve!
General Tips
Be prepared to spend more than the stated 25USD per day - stuff just mounts up, especially when doing expensive activities such as Quads & White Water Rafting.
Take an MP3 player with you if you have one, as it is nice to inflict your music taste on other trip members sometimes :) (but dont go and buy one just for the trip!)
Try to pack your bags so that anything that smells (soap / toothpaste etc) is in one bag - this makes it easier to take out at night and put in bear bins.
Be open minded! There will be quite a lot of new stuff and people, so try not to be set in your ways!
Finally, go on the trip! Everyone loved it, and if you are considering doing it, then the chances are that you will love it too!