For as long as I have been a trainer, this is one of the most common questions, do I do cardio first, or weights first. There is the simplest of answers that if you do weights first you will be tired during cardio, and if cardio first you will be tired during weights. Obviously, if you are training for an event you will want to get the most out of your cardio, or if you are wanting a good strength session, make sure you are strong for that.
http://www.livestrong.com/article/501547-is-it-better-to-do-cardio-before-or-after-lifting/
