A good idea is never miss a warm up:
http://www.pponline.co.uk/encyc/warm-up-exercises.html another good idea- don’t stress it up, if you feel pain- don’t ignore it just like you won’t ignore a fire alarm.
Talk to a certified trainer and build a work out plan. Don’t just start running and lifting weights.
It’s very good you started exercising, you just have to do it safely.