Fine line between under and over packing...
For the record: I under-packed, but I didn't know what to take!
I would bring along:
Medication: if I took any. Basic ones like Ibuprofen or Tylenol, etc.
Spices: there aren't very many Mexican-cuisine spices or foods here. I was able to find a chicken seasoning that is similar to the consome de pollo we put into rice back in the states. Bring Tajin if you're a fan.
Notebook/journal: for class, but also if you have a reflection journal, bring that.You'll find that life moves too slow here, and you won't always have access to WiFi unless you have the money to do so. Physically writing, everything from notes to random thoughts, does a world of difference.
Pots/Pans/Things to cook with?: there is a group of Chinese students who were very efficient and brought cooking-ware from home. They brought everything from chop sticks to a cooking top stove.
Mosquito Repellent: they're mostly active and most vicious at night. If you're going to sit outside at night awhile, apply it thoroughly.
Travel-undershirt fanny pack: easy to hide and very good material that can hold everything from your Ghanaian Cedis to your phone and WiFi box.
At least a couple pairs of fancy outfits: including heels or wedges or something you can dress up and down. This includes a dress or skirt, or whatever you're comfortable going out in. Reality is: YOU ARE GOING TO GO OUT. It's impossible not to. The night/weekend-life culture here is an experience you will want to have.
What I wouldn't pack:
Boots. No one wears boots. Sure it rains, but your feet will be too warm to wear boots. People wear sandals, walking shoes, etc. on a daily.
Water bottle: you'll find that the easiest way to get water is in a bag. They're everywhere, and the cheapest water around. Ask the front desk of your building. They might sell the water in bundles are cheaper.
Heavy jacket: maybe one. You don't really need it. If anything, bring a raincoat, and some light sweaters that would be comfortable in heat and humidity.
Less turtlenecks: they're comfortable if it's a bit windy out and you feel like you're getting sick. Otherwise, forget about it.