This thread gives a few pointers on using the 'Make Market' button and it also has a link to a video tutorial too
viewtopic.php?f=47&t=12967
Im not sure what you mean by asking to stake again (unless you mean you get a pop-up window asking you to confirm your bet?)
If it's not that pop-up window once you click a figure in the P/L column the relevant bet should be sent to the market at the odds shown and if matched you will of greened up for the amount that was shown
I can't remember the exact % off the top of my head but think its something like 96% that you can open any random trade and end up in some sort of profit at some time, however the remaining few % is what will cost you when the times comes and the price just keeps moving away.
What you should be doing is have an amount or number of ticks in mind your prepared to let something move against you and stick to it, and under no circumstances ever allow it to go in-play.