The hip flexor stretch Emily suggested is great and bridging with something to squeeze between your knees is great too. The idea is that whatever you are squeezing keeps your hips in neutral alignment, a yoga block works well. These both help with hip flexor tightness.
Here's another, more neutral example of the same stretch.
I've tried to find a video to illustrate an exercise I have my patients do where they walk with a theraband wrapped around their leg all the way up to the waist to facilitate normal gait, but I can't find one. I may have to make a video myself. eeeeek. It's really hard to teach patients in person, I'm not sure it's possible to describe. You take a really long piece of firm (blue or stronger) theraband. Step on the band at the half way point. pull the band tight +++ and cross it in front of the ankle. Pull the band tight +++ and cross it behind the knee. Keep pulling tight and cross it in front of the hip, then tie it around your waist. With the theraband on like this and walking around, it will help you relearn how to coordinate your muscle activation patterns to bend appropriately when you lift your foot to step forward and also to activate the extensors when you're standing on that leg.