For cases of two possible outcomes, for example, a tennis match, over / under football, etc.. is easier to see when these situations occur, and you can even make a table of equivalences back / lay for use in the homes of exchange and will also serve to check if this is a safe bet.
Also on many websites you can find calculators that make it easy, give the percentage of profit and also indicate the amount to bet on each possible outcome. There are also numerous sites that offer their services to find safe bets, different prices and options, some of them free. Before paying, you should use the possibilities of product testing.
To take advantage of these prices you need to own a lot of money spread over many bookies. It is also a task that involves spending too much time staring at the computer. Therefore, it is not easy money, not only for the time needed to use it for some features of betting.
First, sometimes the prices that are offered can be the result of a mistake, especially when the percentage of profit is very high, and we can cancel the bet. In that case it is important to cover, even losing money, as not worth the risk.
Second, some bookmakers contributions change with great speed and can happen in the same time to make the safe bet is no. We must act quickly and intelligently so that this does not happen third and very important, betting rules are not the same in every home and that can make us lose our sure bet turn into something not 100% sure and we all know Murphy's law.
This aspect is obvious in most of the websites and forums when it comes to this issue and is critical. Therefore, to avoid disappointment we see for example how dropouts are valued in tennis matches, if the extensions in each sport have or not, etc. Fourth, it is best to use only recognized bookmakers. Not worth the risk of losing our money to win a couple of bars sure bets euros.