Always vary your routes and times.
Busy routes are much better. I never use secluded areas at night. Busy areas = lots of people if you need help if you are injured etc.
Never, for the love of God, ever, use headphones.
Do not have your mobile, iPod etc with you - you are a target for muggers or opportunistic scally.
Always wear an ID band with your ICE contact details, medical conditions etc.
Always run facing oncoming traffic but cross to the widest side of a bend.
Never run through a herd of cows - if you separate a mother from a calf you will be in serious shit and it won't be the shit on the floor. Same applies to horses. My personal preference is to never run through a field with a bull.
Wear hi-viz.
Do not engage with weirdos.
Keep you keys in your bra so that you can grab them quickly and use as a weapon by holding them like a knuckleduster. No-one can accuse you of having a weapon - it's your keys.
Use a head torch in the dark, even if you wrap it round your wrist. Also - I use wrist and ankle flashy things - dead cheap from Aldi.