Hardening off tomato seedlings!

Anyone have a good step by step procedure for hardening off pampered tomato seedlings? Should it start in the early morning or late afternoon? How long should they be protected from direct sunlight? Once they are hardened off, and then spend another week under the lights, will they need to be hardened off again.

I grew some rather large plants during the winter to experiment with. I took them out side for about an hour in the direct winter sunlight and they got sunburned. I want to be careful with the seedlings I will be planting in the garden to prevent sunburn.

Thanks

Ted