1) Make it easy - Buy containers that are easy to open, and practice opening them at home. If children need to wait for someone to help them open containers, they are likely to run out of time, and they won't finish their lunches.
2) Pack what they like - As much as you would like them to eat a perfect lunch, the truth is that they are not likely to eat things they don't like. Work with them to come up with healthy options that they want to eat.
3) Eat more at snack time - From my experience, kids want to eat their lunch as fast as they can so that they can get outside and play with their friends. In the past, my boys have tried to eat bigger portions of their lunch at snack time so that there was less to eat at lunch time. If this is an option for your little ones, you should give it a try because it worked for my boys.
4) Save dessert for last - The rule in our house is... "the treat in the lunch box doesn't get eaten until all the healthy food is gone". This is a big motivator for my boys. If they break the rule, there is no treat in the lunch box the next day.
5) Don't worry - If you little ones eat a healthy breakfast and a healthy supper, don't freak out if they don't eat every bit of food you pack in their lunch boxes. They'll eat if they are hungry, and the best you can do is pack them a healthy lunch and hope they eat it.
I hope you find one or two of these tips helpful. Do you have a tip that works for you? I'd love to have you share it in the comments.