Creatine has been proven many times to be beneficial when lifting weights. 5g is the standard reccomended dose for the average sized person. As BTB stated he takes more, as do I, both of us bigger than average. I usually go between 7-10g a day when I am taking it. I only stopped when I was on break from the gym. That changes soon enough..
Anyway, there is no need to load for days prior; and it doesn't matter when you take it, as long as you are consistent on dosing times so your body can make it's own adjustments to utilize the creatine. Also, I highly recco getting a Creapure certified brand. Creapure is a trademarked name for either pure German creatine, or creatine made with the same process, resulting in 99% pure creatine, no fillers or other additives/impurities. I can say Allmax is a good brand, as is ISS. I actually have a tub of both in stock right now. The ISS is almost gone, and the Allmax will replace it, only because it was on sale.
And don't forget to increase your water intake, or you could get some bad cramps. Bloating is also a possibility, but it won't make you fat. Again, your body will adjust over time.