sounds like 'guy' advice
and there's a couple of girls (namely a shoppie and a spa chick) who can't go without packing A LOT!
It's taken me five years to get packing down to a science - so here's my tips
For your first contract - take one large suitcase, one big carry-on. Make sure you can handle moving/carrying both by yourself easily, as YOU are going to be dragging them up and down the gangway yourself (or between customs at the airport)
Start by piling everthing you use in the course of a day as far as toiletries/cosmetics/hair - just like you're going to work. Don't forget shaving, washing your hair, etc. Then add in anthing different you'd do for a nice night out at a night club or dinner. If you're concerned about weight, take only what will last for 2-3 weeks, as you'll be able to buy more.
Clothes, this will be hard! Remember you'll be wearing a uniform most of the time. Take at least 2 weeks of underthings. At the most two outfits each of going out in a port (casual) and formal. Formal - one simple dress/shoes you can work in (not to strappy or revealing) and another your choice. Maybe one more that you can do 'dirtier' work in (unpacking boxes, cleaning). AND THAT'S IT. Your time on a ship will be mostly working, then going into crew areas to eat, or relax at the crewbar or internet cafe, or going 'out' into pax area. You don't need to bring a lot of extra clothes. Don't pack anything extra, but have it maybe boxed or in a pile that you can tell a friend or relative to 'send me that . . . '
As far as anthing else - cell phone (you can always get a 'pay as you go' phone in your home port and get phone cards), MP3 player. Laptop if you have one. Very important are photos or anything else that will remind you of home (family, friends, pets)
Anything else you can buy in a port. Really! You're probably going to be buying different clothes anyway and you can buy another suitcase when you're out there also. You're going to have a really, really small closet and maybe 2 drawers to put your things into, so try not to bring a lot.
One of the best things I got was one of those roll out/hang up cosmetic organizers, and a soft make up case. Everything 'girly' I need goes in those two items. If it doesn't fit, something else has to go or it doesn't go.
When you do your final pack, make sure that 4-5 days worth of undies/plain clothes are in your carry on as the airlines have been losing a lot of luggage lately. Check what the current restrictions are on liquids and make up so you're legal and pack everything else in your checked luggage.
hoping this helps a little. After all this time, I still pack things I don't use or don't wear.