I have a vial of white labs yeast which I will be using today, it states that it has the correct amount of yeast for a five gallon batch. I have been reading a lot about making a starter but if its not necessary why would I want to add another step? From what I understand it just reduces lag time? Am I missing something should I be making a starter?

In theory, the White Labs tube you have should be fine.

I only recommend making a starter when using White Labs yeast simply because unlike the Wyeast smack packs you have no way of knowing if the yeast are viable or not.

I've know people that have used such yeast which apparently had been mishandled somewhere along the way and were not viable.

- Scott

Even White Labs recommends making a 'proof starter' with their vials prior to pitching. This is basically a very small starter that you'd make the night before you brew your beer, which will let you know that your yeast are viable and gives you the added benefit of getting them energized and active before you pitch them to your main wort.
Having said that, I will tell you this. I've never made a starter for White Labs yeast that I've purchased from Northern Brewer and used right away. Lag times usually run from 8-12 hours with aeration from an aquarium pump.
Before you decide for yourself what to do, just remember that a starter is extremely cheap insurance, to ensure yeast health, When compared with the cost of a ruined batch of beer.

Cheers
Dave

I never made starters when I started brewing with White Labs. I always had good luck. I still use White Labs and now I always make a starter. Yes, it is an extra step (or two or three if you're pitching a 1/2 gallon starter), but to me it's totally worth it. Shorter lag time means there is less likelihood that a wild yeast that may sneak into your wort will stand a chance of ruining your beer. I consistently pitch big starters and seen bubbles within half an hour. (Occasionally I get a lazy yeast (WLP002) that takes a little longer.) Even when I repitch I always add about 500 ml of sterile wort to my jug 'o' yeast the night before just to wake the little yeasties up.

how exactly do you make a starter, and can u reuse yeast at the bottom of a fermented batch to save on purchasing? if u do reuse would that impact the flavor or a different recipe by using a small quantity of old beer with the yeast in it?