I think this will only partially answer the question as I don’t use press releases for my betting sites – mainly because they are only a side income.
However, I use press releases all the time for my main business. My company owns around 20 business to business websites and we put out an average of two press releases per week.
Rule of thumb: only put out genuinely newsworthy press releases. Secondly, if you don’t have someone in house to write your release, then hire a professional.
I know I’m probably going to regret this, but the guy over at PRUnderground (http://www.prunderground.com ) writes top class press releases that will get you featured on sites you didn’t think possible.
You need to choose the platinum package, which is a fraction under $50. That gets you a well written press release plus distribution via their network. You can, of course, then submit it via PrWeb, PrNewsWire and so forth.