Can anyone help? I just opened an internet account with TDWaterhouse and was wondering how the stop loss facility works.

With ComDirect you can set a price that they will automatically sell at if the bid price drops too low - usually 10% below the current bid I think. Can't be higher though. You can up it as / if the price rises. Only thing is some shares have VERY wide spreads on a morning so watch out. I personally would rather keep watch regularly and not risk selling if there's a sudden short gap in the order book and the price drops. I always look at the news before 8 am on a morning. As an example I made quite a lot of money earlier in the year - was holding SFW and they'd been going down. Set a limit sell if they came to breakeven. Read the MRW takeover news pre 8am, cancelled the limit order and rode the wave to (nearly) the top then sold. If I hadn't read the news I'd have made next to nothing.

You've got to keep one step ahead all the time and plan.

ticker - There are widely differing stop-loss mechanisms between differing brokers.
You need to get exact details of the functionality from your own broker, to be sure you are happy to use their facility.

e.g. With comdirect the stoploss works on bid alone, so a cheeky extremely low bid on a SETS stock at market opening, may sell your stock automatically for a very poor price. You will also find that, if there is some news that causes your stock price to drop rapidly, the RSPs drop the online trade quantity, so your order may still fail to trigger due to being over the new lower online trade size.

Other brokers have more complicated algorithms that check the spread as well, to avoid this situation.

Personally, I don't use stops but your decision will depend on how much time you are able to spend monitoring yopur portfolio.