Thanks, this worked! Just in case other noobs like me come across this thread I'm going to modify your instructions.
In order for my modified instructions to work, the server files need to be located in your home folder. Also, I'm assuming your server folder's name is TekkitServer.
1. Open up TextEdit.
2. Click edit and then Change to Plain Text (or the like)
3. Type the following:
cd ~/TekkitServer
java -Xincgc -Xms777M -Xmx1024M -jar Tekkit.jar
4. click save as, then untick the thing that says if no extension is provided, use ".txt" and name it Launchserver.command
5. Save it to the same folder as your home directory (click on your computer's name in finder, that is it)
6. Open Terminal. (Applications/Utilities/Terminal)
7. Type chmod +x
8. Make sure there are two spaces after the +x and then drag the file you just made directly into the Terminal window.
9. Press enter (return)
10. Now if you don't know Terminal well, it might look like nothing happened. Close Terminal and then double click your Launchserver.command file. If you have Java 7 and the versions are in the correct order, the server should run fine!
11. For other common server problems, see the "Bugs and their Fixes" section of http://forums.technicpack.net/index.php/topic,1938.0.html
Let me know if I made a mistake in these instructions, I'd hate to mess anyone up!