Here is my two-cents worth.
1) If you're not trading, this makes you more attractive to a dealer because they don't have to acquire a unit to offload a unit. however, if you are trading, know that the trade difference affects the sales tax you pay on the new one. this especially helps if you're trying to figure out OTD/payment numbers.
2) If you're financing, this makes you more attractive to a dealer because they'll get an additional bump from that. That being said, check what you're eligible for with your personal bank/credit union first to get a ballpark on the interest rate you're good for so you know if a dealer is fishing you or not - they're not above doing this.
3) Be willing to drive. I have driven as much as 300 miles for the vehicle I wanted. Familiarize yourself with the inventory in that radius. The more options, the better. You're at a dealer to extract the best offer from them, so you have to acquire as much leverage as possible to play their game better than them

this is the internet age - local only works for you if the price does.
4) keep a p0ker face for negotiation. you need them to think you're fairly lukewarm toward a purchase until after the papers are signed.
since I'm completely slow at work today, I did you a favor:
Edmunds offered the following information regarding a 2014 Focus ST (whichever the base without options is):
The MSRP is $24,940 while the average price paid is $23,352. This tells us a few things, the most important of which is that the vehicle isn't WRX status (you're going to have to pay MSRP because the demand is so damn high on a WRX and there's not much supply to curb the demand, meaning dealers don't have to budge on pricing and their profit is max). Dealers are discounting the Focus, which means there's bargaining room for you. The average is $1500 below sticker, apparently.
Cars.com is a great place to search and narrow down results.
New Focus STs in the US, sorted by cheapest to most expensive.
You'll find that the leftover 2014s are pretty deeply discounted across the board. Use that as a reference level, and narrow down the ones closest to you and go from there.
Rock on.