Fill the bladder 1/2 to 2/3 full of water. Then blow air through the hose to fill it up like a balloon. Lay it down in the freezer and just store it there until you are ready to ride. When you want to ride, top it off with cold water, put it in the pack and off you go. The cap may be hard to open if it's frozen shut - just run some hot water over the cap until you can dislodge it. It won't be enough to melt the giant ice cube in the bladder.

Topping it off insures the hose is not blocked by ice, and gives you water to drink right away. The big block of ice melts slowly, and delivers cold water for up to 3 hours at 80-90o temps. The pack may seem stiff when you first put it on, but the edges start to melt, and it conforms to your back. After a few minutes you don't even know it's there.

Oakleaf also mentioned my favorite tip - after you take a drink from the hose, blow air back into the bladder. Otherwise the water in the hose gets awfully warm. If I forget to blow the water back up the hose, I will usually spit it out. Drinking warm water is one of those gross things I can not consume on a bike ride.

When you get home, give the bladder a good rinse, wash the bite valve and rinse well (you don't want a soapy gulp of water on your next ride). Fill the bladder 1/2 way or more with water (I use filtered water from Brita pitcher) and back into the freezer until the next ride.

I only put water in the bladder - never mixed stuff - keeps everything easier to clean. Use water bottles for your mixes.

Keeping the bladder in the freezer also keeps it free from mold or nasty bugs, and you don't have to worry about drying it thoroughly.

I've been using this systemn for years - works great. I have the "Rogue" model, holds 70 oz. I rarely drink it all but on a few rides I have replenished the reservoir (metrics in 90o+ - who ever thought that was a good idea?)