My advice:
Use a water tight container - don't use gladware or anything else that was meant for temporary food storage and isn't water tight.
How are you going to get your coordinates? Do you know how to average? Get the most accurate coordinates that you can. If your coordinates are fuzzy because of tree coverage, give a good hint so people can find it without trampling around too much.
Stick close to your computer the first couple of days that your cache is published and be prepared to correct any problems. If cachers tell you your cache is 60 meters from ground zero and give you a more accurate coordinates, consider editing your posted latitude/longitude coords. If you can't figure out how to do something with regards to editting coords or cache description ask your reviewer and/or ask here on the forums for help.
Getting the right coordinates is a concern of mine - I am using my iPhone and it always tells me "accurate with in 56 ft" - I don't want to give someone the wrong coordinates because my iPhone is off