I can only speak for Etrade.
With margin on the account, I don't have to wait 3 days after I sell something to use those funds.
I could buy AGRT today, sell it this afternoon, then buy GWBU right after that, then sell it 5 minutes later, and turn around and buy AGRT again, then sell it again. After those 3 day trades I would have to wait 5 trading days before I day traded again, but I could buy and hold over night and sell it the next day. Or you could do your day trades on different days. You don't have to wait the 3 day settlement time if you have margin. Just don't make more than 3 day trades in. A 5 trading day period.
Etrade has a counter in the balances section of your account page which tracks how many you can do, and have done. I don't know if other brokers do that for you or not. I think it's good that it's displayed, then you don't wonder if something you traded counted as a day trade or not, it's right there for you to look at.
