I can burn quite a few calories when I am out walking. Here's what I do:
*Vary the pace (intervals and recoveries)
*Pump my arms at the speed I want my legs to go
*Keep my rear and gut sucked in
*Deep breathing in and slow exhales out (in for four, out for four)
*Turn it into a circuit by throwing in something every 1/2 mile, like jumping jacks, push-ups, high knees, squats, lunges, etc (yup, I look stupid, but I choose to think others who see me think I am "in training")
* Play "Simon says" if I am walking with DD...we have to do whatever the other says....DD can get kinda rough with her orders, but we make it fun!
*I have carried light hand weights (3-5#s), but didn't see alot of difference in calorie burn, and I got tired faster. I don't think the risk to the elbows & shoulders was worth it, personally. I tried and discarded the idea of using ankle weights. They flopped on my ankles.
*Walk backwards
*Change routes and surfaces. I walk either on grass or gravel trails, but have done concrete as well. Not too good on concrete if you are prone to shin splints or have poor shoes.
*Use imagery: like I am in a race, or being chased...
Not too original, but maybe there is one or two you haven't tried or thought of.....
HTH, Julie