Congrats on the news about Part 1! You will have fun!
1. Tarps or towels are a good idea. No matter how hard you try you will make a mess.
1.A Get help! Even if they are there to just take pictures and make sure they know how to work the camera. If my brother wasn't here when I got Part 2 I would have never got one of the rocks in the tank or I would have had to break it all apart and I didn't want to do that.
2. Get a Brute trashcan and only Brute. They are NSF approved and won't leach anything into the water from the plastic the can is made from. How many 5g buckets do you have? IMO you need at least your tank capacity on hand of fresh SW that is up to temp for water changes. More for swishing the rocks because after swishing you strain for hitchhikers and dump that water.
3. I got some plastic bins that were about 12" tall to put the rocks in before they went in the tank. I put the fresh SW in them so I could swish them and examine them better this way than in the bags. It is also easier to pick them up and down because the rocks usually aren't too light.
4. Smell every rock! and rotate it as you smell it! Anything that doesn't smell right rub it off. You will know if it is dead because there is no mistaking the smell. I made sure I did this and I had virtually not ammonia spike on either part.
5. Remove any know bad hitchhikers. They are harder to get out later and no matter how hard you try you won't get them all. Anything questionable keep them separate or put them in your sump (if you have one) until you know for sure. Dispatch of any gorilla crabs right away!

Porcelin crabs are the only crab I would let in my tank. Any other crab you will want out later and it can be a real pain. Since I'm on the crab thing, IMO when you call for part 2 ask them for something else or more snails instead of hermits. You don't need them and they cause more trouble then they are worth. If you must have some only get a couple.
6. HAVE FUN!!!! I remember how exciting it was when my rock came.
6.A Look at the rock well before you put it in to determine what side is the bottom. You don't want to bury any cool stuff on the rock in the sand.
7. Don't be surprised if you want to keep rearranging the rock around the tank because after it goes in you won't be able to see a thing.
8. TAKE LOTS OF PICTURES and the most important part DON"T FORGET TO POST THEM!!!!!!
