Removing And Re-Uploading Shop

I need to take my shop offline and then upload it to another web host.

Can someone walk me through the correct procedure for this, so I don't end up messing it up?

Hi, generally speaking it is not a complex operation. Main point of attention, IMHO, is regarding dns reconfiguration. I suppose in fact you will maintain the same domain in your new host. Am I right?
Said that, if you have your new host already available, the process is the following.
1) put your site in maintenance mode
2) Clear all caches (not strictly required but you can save a lot of space / bandwidth)
3) backup your files (you could even zip your public html folder, if you use cpanel, plesk or ssh)
4) backup/export your MySQL db
Then, on your new host :
5)Copy your files in new public html folder
6) Create / Restore the db
7) Update paths in config. php files in the main root and in admin folder.
to test if everything is ok, before real migration, use another domain or modify your pc local hosts file in order to point your domain to the ip address of your new host.
9) If everything is right, update dns configuration to point to new server.
Please take into account this last operation can take hours to complete propagation, so plan the entire migration process in a low traffic period (night or week end).
10) Leave maintenance mode... and go!

M

thats a great tip!

"modify your pc local hosts file"

glad to help you, I performed these operations really a lot of times...