I don't know how good this picture is, but here is one of my dinnerplates that I have staked with a wire stake. I buy my wire stakes at Walmart for 4.97 each. They work really well.
http://i14.photobucket.com/albums/a307/Mexley/f97ce95e.jpg

Thanks for your reply. I bought the tomato cage. The dahlias are well grown and so I had lot of trouble constraining the plant in the cage. Not sure if this is a recommended method for a well grown plant. The other option is to buy the bamboo stake and tie the plant. Any suggestions?

Well, it is according to how tall your Dahlias are, and how large the stalk is. That is why I like the wide wire stakes. They are about 4 bars wide, are very study, and are tall enough to hold up the Dahlias. I have had Bamboo stakes to blow over, and tomato cages are not tall enough for my dinnerplates.

this year I bought the Texas Tomato cages for half my tomato plants (they are wonderful and my only cages to hold up with all the weather we've been having)...anyway, this year I took all the old cheap cages and cut off the 4 prongs, turned them upside down and used the leftover prongs to hold the cage in place and so far none of my dinnerplate dahlias have toppled

I read some sensible advice somewhere that said you should put your stake in the ground when you plant the tuber, so as to avoid damaging the tuber later. It also means that you start tying in the stalk earlier, not just when it has broken or is about to, like I usually do!