First, and most importantly, you need good containers. I would recommend starting with containers from http://www.easylunchboxes.com/. These are hands down the best, easiest to use lunch boxes ever! Besides you can get a lot of food in them! Lunch Bots are great too, and come in a variety of sizes and compartments. http://www.lunchbots.com/ The Container Store carries a large variety, but none of them are favorites here. Sanrio (the makers of Hello Kitty) make wonderful bento boxes, and most include silverware! http://shop.sanrio.com/hello-kitty-lunch-case-with-utensils/59810-201008,default,pd.html Finally do a search on EBay and Amazon for bento boxes, you'll find some great, genuine bento boxes. And don't forget to shop at local Asian and Japanese markets.
You'll have lots of choices and you'll want to experiment. Some days you'll want to pack a smaller lunch but include a thermos for soup or pasta. If you don't have a way to heat hot foods, you'll want to invest in a Thermos as well.
Separating foods might not be important to every one, but my girls really prefer things not to touch. So I use a lot of silicon holders. I initially bought the Wilton brand, they are readily available, but expensive. http://www.wilton.com/store/site/department.cfm?id=DA7CB637-423B-522D-F493CCF30B9364A2&fid=DA7CB657-423B-522D-FA96208D65BFD2EA
I've found that Cost Plus World Market has some great options; lots of colors and shapes and they are very reasonably priced. I believe your get 6 holders for about $2.50. Also the Japanese Grass that is used in sushi trays is fun to use and changes up the look of your lunches! http://www.japanbargain.com/servlet/the-1570/Sushi-Balan,-Sushi-Baran,/Detail
Cookie cutters of all shapes and sizes will add to the fun in your lunches and will have your little ones wondering what lunch will look like each day! Use them to create a theme, and to cut veggies, fruit, sandwiches, cheese...the possibilities are endless. I think that the metal cutters work best, and you'll want a variety of shapes and sizes. For example I have about 15 different heart shaped cutters, they range from about a half inch to 5 inches.
Food safe pens will allow you to draw faces, add details and write notes to your kids on their food! They'll really get a kick out of it and so will their friends. Your child might not love cheese, but what if the had a little Baby Bell circle colored like a soccer ball? That might make them brave enough or interested enough to try a bite or two.
Picks and decorative forks are the final layer of fun. If you do a search for bento picks on Amazon hundreds of these darling little guys come up. The selection is amazing...from zoo animals to stems and leaves...if you can imagine it, they sell it. Don't overlook The Dollar Tree and your neighborhood grocery store. Holiday cupcake picks are a great addition and they're generally pretty inexpensive. The Dollar Tree sells holiday tick tack toe games, I buy them then throw out the game board, your left with 10-12 darling holiday picks that I can use over and over again. At the grocery store you can find frilly tooth picks, pirate swords, bamboo sticks, and Wilton cupcake picks.
And finally, make it fun for you too! You have to pack these little cuties, so make sure your enjoying it. Love notes on a not very fancy lunch go a long way in dressing it up, treats that are holiday themed will bring squeals of joy, just cutting things into little pieces and using picks can dress up a lunch, and as I find great things I will always share where I've found them!