This all comes down to personal criteria of course but for me it takes a while to get properly ready and primed for a run. If I am running on the road I would definitely wait for that window of opportunity where the weather is just right or the roads aren't too wet (especially in these days). Even temperature wise, being a student does give me some benefits in this regard, meaning that I decide for myself when I go for my run, I usually take early afternoon so that the weather would be a little bit warm (in winter) and so it won't be such a sock to my body for both before and after the run, although during the run after the first 1 or 2 km all feeling of coldness would be taken away.
Nutrition wise (before any nutritionist goes nuts I would like to say that I know it's wrong) but I usually eat something very light way way beforehand or even sometimes nothing at all. The day before I drink plenty of water and herbal tea but I read that you may continue to drink up to two hours before any run otherwise you'll be dodging in the bushes throughout the run, but as you start running you can consume as much fluids as you wish. And don't forget the numbers 1s and 2s ;-).
Physical preparation over, mental preparation is perhaps the most difficult to do especially when starting up in my opinion. Tell any person that you did a 10km run today and they'd raise their eyebrows. But why is that? I mean sure it takes a while to be able to do that way under an hour but why do many people see this as such a large distance? Mentally you just split this distance into intervals according to the route you take.
So I say this to anyone who wishes to start running; don't give up every stage of your training is important even if you just run for 5 minutes, that 5 minutes might someday snowball into 10, then 20 then an hour and perhaps even a marathon. Rome wasn't built in a day =)