you can start with a with the basics ..., check your main relay . then ingnition compents ( mainly the ignition coil ) then move on to your fuel pressure. .. if the problem is still undetected.. try a compression test.. does the car start better when it is already warm?...or is it only happening when it is cold?... pull out a spark plug .. what colour is it?
does your car have a rough idle when it does start?