Check local prices before ordering on line. Just saw ammo at Walmart (.223) for less than I could order it when considering shipping.
True, sometimes. But, for me... if the difference in cost is just the shipping, I go the online route rather than drive around town. Don't forget that if you buy locally, you add in sales tax. So, sometimes it's a wash. Again... I love that it shows up at my door rather than having to get in my car, drive at least a half hour round trip, deal with traffic, deal with people at walmart, deal with WAITING for the walmart staffer to get the key and open the case... and so on.
With online shopping, I can do it in my underwear while watching Leno. Then the "brown truck of happiness" shows up at my door with my goodies. It's just so much easier.
Oh... so far, I've used (with good results and in no particular order):
SG AMMO
Ammunition to Go
Cheaper than Dirt