how do we solve diamond problems

When we have a problem like

ex.// 

x^2-2x-99

1. we have to make a lager X
2. then place the two numbers (-2, -99)
3. then place it in the X 
4. place the -2 on the top of the X and the -99 on the bottom
5. we have to find out what two numbers add to -2 and multiply to -99
6. we list all the multiply of -99 which are (1,-99),(3-33),(9,-11),(11,-9),(33,-3),(99,-1)
7. now we got to add them to find which will equal -2
8. after that the two number placement doesn't matter 

this is another example