My wife and I go out often, and I go out alone also. We have have gone shopping in towns that (I found out later) were very conservative, and I've never had any negative reactions directed at me. I've noticed men looking at me as I walk by, but have decide to assume its because they like what they see! (lemon aid from lemons). My worst experience was self-made, I locked my keys, purse and phone in my car at a gas stations! But had no problems while waiting inside for help.
In addition to all the great advice, I'd add:
Stand Up Straight and Hold Your Head High
And Wear Clothes that are COMFORTABLE and Fit Well (If you're fighting with your clothing, you'll make yourself a nervous wreck and draw more attention)
