While I get behind that strategy every once in a while, I don't usually like it. I'm a fresh flower kind of girl. Potted, cut, I don't care. Give me flowers. And NOT silk ones. But flowers are expensive. So how can you have fresh flowers at your event AND not blow your life savings on them?
Here are some ideas:
Hit up your local grocer. Tons of supermarkets have a pretty decent selection of flowers, and they're not just for the impulsive shopper that *only* ran out to get some milk. Turns out, they're often able to pre-order and arrange flowers...if you ask nicely.
Try farmers markets or produce stands. I was able to get enough flowers for around 15 tables for less than $20 at Produce Junction. I gussied them up by putting them in nontraditional vases like cocktail glasses, and even poked some feathers in (it was a glamorous night). Of course, this option works if you're willing to deal with what they have. Hitting up a farmer's market the morning of your event won't guarantee you a gross of, I don't know, yellow dahlias, for example.
Check out the flower market. Check to see if your city-- or one near you-- has a flower market. The Boston Flower Market, for example, is a great source for a huge inventory of wholesale flowers.
Go online! If you can't pick up your flowers in person, check out Blooms by the Box, an online retailer of wholesale flowers. The also have video tutorials, should you need assistance in arranging or tying, and even prearranged flowers, in case you're need more than a little help! I was recently at a wedding with Blooms by the Box centerpieces that looked GREAT. Perhaps the bride will stop by to drop some knowledge on us later...
[a Blooms by the Box customer creation]
Buy what's in season. I can't stress this tip enough. I mean, do you eat peaches in winter? (Local peaches in North America, that is?) No. Because they're not as good, and they cost much, much more to get them off-season because they come from somewhere way across the globe. So it's important to research what flowers will be in season (around you/your event) at the time of your event. Here's a nice, basic round-up of what's in season and when.
Mix floral with non-floral. I mentioned adding feathers to some centerpieces. You could also go with twigs/sticks/branches, grass, pumpkins...get creative! The more of the other stuff you use, the fewer flowers you need in each arrangement-- but they're still represented.
[can I just say how in love with this birds nest I am?]