Proper maintenance (oil changes every 3,000 miles) use a good oil (Castrol GTX), Don't buy cheap gas (I always use Shell), Don't "Drive it like you stole it", Winterize Your Car, spark plugs should be checked approximately every 10000 miles and atleast once a week drive for about a half hour...
Your starter, solenoid or the battery needs a charge! Last thing, and is not likely it, the car is not fully in park...but I don't believe it would even click!
in the long run you will increase mileage, but as warrior stated, you will need a shorter belt, could run you around $20, I personally would leave it on..but if you are really wanting to conserve fuel take it off!
if it sounds like it barely has enough power to turn the starter then 'd say battery, if it fails to engage the starter could be battery or starter, if it cranks fine just does not start I'd put a pressure guage on the fuel rail/line to see if it's getting enough pressure to the injectors
if you take your battery to an auto part store they'll charge it for you for free, I've heard of the risks of jump starting vehicles before....but have never had a problem doing so! another option is starting another vehicle that has a top post battery, while that car is running carefully...